Please answer the following question: Information:  - The Boston Ballet is an American professional classical ballet company based in Boston, Massachusetts. The company, founded in 1963 by E. Virginia Williams, and Sydney Leonard, was the first professional repertory ballet company in New England. Boston Ballets national and international reputation developed under the leadership of Artistic Directors Violette Verdy (19801984), Bruce Marks (19851997), and Anna-Marie Holmes (19972000). Today, Boston Ballet is one of the major ballet companies in North America and among the top companies in the world. Current Artistic Director Mikko Nissinen was selected to lead Boston Ballet in September 2001. Under his artistic direction, Boston Ballet maintains an internationally recognized repertoire of classical, neo-classical and contemporary works, ranging from full-length story ballets to masterworks by George Balanchine, to new works and world premieres by contemporary choreographers. Nissinen leads the company, and Boston Ballet School, the largest ballet school in North America, with Executive Director Meredith (Max) Hodges.  - Léon Eugene Barzin (November 27, 1900April 29, 1999) was a Belgian-born American conductor and founder of the National Orchestral Association (NOA), the oldest surviving training orchestra in the United States. Barzin was also the founding musical director of the New York City Ballet.  - Lincoln Edward Kirstein (May 4, 1907  January 5, 1996) was an American writer, impresario, art connoisseur, philanthropist, and cultural figure in New York City, noted especially as co-founder of the New York City Ballet. He developed and sustained the company with his organizing ability and fundraising for more than four decades, serving as the company's General Director from 1946 to 1989. According to the "New York Times," he was "an expert in many fields," organizing art exhibits and lecture tours in the same years.  - The School of American Ballet (SAB) is an American classical ballet school and is the associate school of the New York City Ballet, a ballet company based at the Lincoln Center for the Performing Arts in New York City. The school trains students from the age of six, with professional vocational ballet training for students aged 1118. Graduates of the school achieve employment with leading ballet companies worldwide, most notably in the United States with New York City Ballet, American Ballet Theatre, Boston Ballet, and San Francisco Ballet.  - Delaware is a state located in the Mid-Atlantic and/or Northeastern regions of the United States. It is bordered to the south and west by Maryland, to the northeast by New Jersey, and to the north by Pennsylvania. The state takes its name from Thomas West, 3rd Baron De La Warr, an English nobleman and Virginia's first colonial governor.  - Ballet Society is a non-profit educational institution founded in 1946 by Lincoln Kirstein and George Balanchine. At its founding, Balanchine was the Artistic Director and Kirstein served as the Secretary. The president of Ballet Society is Nancy Lassalle, an original Board member of both the School of American Ballet and the New York City Ballet, currently Emerita.  - Classical ballet is any of the traditional, formal styles of ballet that exclusively employ classical ballet technique. It is known for its aesthetics and rigorous technique (such as pointe work, turnout of the legs, and high extensions), its flowing, precise movements, and its ethereal qualities.  - New York City Ballet (NYCB) is a ballet company founded in 1948 by choreographer George Balanchine and Lincoln Kirstein. Léon Barzin was the company's first music director. Balanchine and Jerome Robbins are considered the founding choreographers of the company. City Ballet grew out of earlier troupes: the Producing Company of the School of American Ballet, 1934; the American Ballet, 1935, and Ballet Caravan, 1936, which merged into American Ballet Caravan, 1941; and directly from the Ballet Society, 1946.  - Sean Lavery , born in Harrisburg , Pennsylvania , is assistant to the balletmaster in chief at New York City Ballet , of which he was principal dancer ; a répétiteur with the George Balanchine Trust ; and a faculty member at the School of American Ballet . Lavery joined the San Francisco Ballet in 1973 and the Frankfurt Opera Ballet in 1975 , where he promoted to principal dancer . In 1976 , Lavery returned to New York and the School of American Ballet . He joined City Ballet in 1977 and his debut role was Titania 's Cavalier in Balanchine 's A Midsummer Night 's Dream . He was promoted to soloist in early 1978 and principal dancer later that year . Lavery was in the original casts of more than a dozen dances at City Ballet , staged the balcony scene from Romeo and Juliet for them and made Twinkliana to music by Wolfgang Amadeus Mozart on Katrina Killian for the School of American Ballet workshop , June 2007 .  - Ontario, one of the 13 provinces and territories of Canada, is located in east-central Canada. It is Canada's most populous province by a large margin, accounting for nearly 40 percent of all Canadians, and is the second-largest province in total area. Ontario is fourth-largest in total area when the territories of the Northwest Territories and Nunavut are included. It is home to the nation's capital city, Ottawa, and the nation's most populous city, Toronto.  - A principal dancer (often shortened to principal) is a dancer at the highest rank within a professional dance company, particularly a ballet company.  - Lincoln Center for the Performing Arts is a complex of buildings in the Lincoln Square neighborhood of the borough of Manhattan in New York City. It hosts many notable performing arts organizations, which are nationally and internationally renowned, including the New York Philharmonic, the Metropolitan Opera, and the New York City Ballet.  - A répétiteur (from French verb "répéter" meaning "to repeat, to go over, to learn, to rehearse") is an accompanist, tutor or coach of ballet dancers or opera singers.  - George Balanchine (born Giorgi Melitonovitch Balanchivadze April 30, 1983) was a choreographer. Styled as the father of American ballet, he co-founded the New York City Ballet and remained its Artistic Director for more than 35 years.  - The Appalachian Mountains, often called the Appalachians, are a system of mountains in eastern North America. The Appalachians first formed roughly 480 million years ago during the Ordovician Period. It once reached elevations similar to those of the Alps and the Rocky Mountains before naturally occurring erosion. The Appalachian chain is a barrier to east-west travel, as it forms a series of alternating ridgelines and valleys oriented in opposition to most roads running east or west.  - A ballet company is a group of dancers who perform classical ballet, neoclassical ballet, and/or contemporary ballet in the European tradition, plus managerial and support staff. Most major ballet companies employ dancers on a year-round basis, except in the United States, where contracts for part of the year (typically thirty or forty weeks) are the norm. A company generally has a home theatre where it stages the majority of its performances, but many companies also tour in their home country or internationally.  - Pennsylvania (Pennsylvania German: "Pennsylvaani"), officially the Commonwealth of Pennsylvania, is a state located in the northeastern and Mid-Atlantic regions of the United States. The Appalachian Mountains run through its middle. The commonwealth borders Delaware to the southeast, Maryland to the south, West Virginia to the southwest, Ohio to the west, Lake Erie and the Canadian province of Ontario to the northwest, New York to the north, and New Jersey to the east.  - Opera (English plural: "operas"; Italian plural: "opere" ) is an art form in which singers and musicians perform a dramatic work combining text (libretto) and musical score, usually in a theatrical setting. In traditional opera, singers do two types of singing: recitative, a speech-inflected style and arias, a more melodic style. Opera incorporates many of the elements of spoken theatre, such as acting, scenery, and costumes and sometimes includes dance. The performance is typically given in an opera house, accompanied by an orchestra or smaller musical ensemble, which since the early 19th century has been led by a conductor.  - San Francisco Ballet is a ballet company, founded in 1933 as the San Francisco Opera Ballet under the leadership of ballet master Adolph Bolm. The company is currently based in the War Memorial Opera House, San Francisco, under the direction of Helgi Tomasson. San Francisco Ballet was the first professional ballet company in the United States. It is among the world's leading dance companies, presenting more than 100 performances annually, with a repertoire that spans both classical and contemporary ballet. Along with American Ballet Theatre and the New York City Ballet, San Francisco Ballet has been described as part of the "triumvirate of great classical companies defining the American style on the world stage today".  - American Ballet Theatre (ABT) is a classical ballet company based in New York City. It has an annual eight-week season at the Metropolitan Opera House (Lincoln Center) in the spring and a shorter season at the David H. Koch Theater in the fall; the company tours around the world the rest of the year. ABT was founded in 1939 by Lucia Chase and Richard Pleasant and is recognized as one of the world's leading classical ballet companies. ABT is also the parent company of the American Ballet Theatre Jacqueline Kennedy Onassis School, and was recognized as "America's National Ballet Company" in 2006 by the United States Congress.  - Ballet is a type of performance dance that originated in the Italian Renaissance courts of the 15th century and later developed into a concert dance form in France and Russia. It has since become a widespread, highly technical form of dance with its own vocabulary based on French terminology. It has been globally influential and has defined the foundational techniques used in many other dance genres. Becoming a ballet dancer requires years of training. Ballet has been taught in various schools around the world, which have historically incorporated their own cultures to evolve the art.  - Jerome Robbins (October 11, 1918  July 29, 1998) was an American choreographer, director, dancer, and theater producer who worked in classical ballet, on Broadway, and in films and television. Among his numerous stage productions he worked on were "On the Town", "Peter Pan", "High Button Shoes", "The King And I", "The Pajama Game", "Bells Are Ringing", "West Side Story", "", and "Fiddler on the Roof"; Robbins was a five time Tony award winner and a recipient of the Kennedy Center Honors. He received two Academy Awards, including the 1961 Academy Award for Best Director with Robert Wise for "West Side Story". A documentary about his life and work, "Something to Dance About", featuring excerpts from his journals, archival performance and rehearsal footage, and interviews with Robbins and his colleagues, premiered on PBS in 2009 and won both an Emmy and a Peabody Award the same year.    Given the paragraphs above, decide what entity has the relation 'occupation' with 'choreographer'.
A:
sean lavery