user: Question: What parties are represented in Massachusetts4 district?
Columns: ['District', 'Incumbent', 'Party', 'First elected', 'Status', 'Opponent']
Types: ['text', 'text', 'text', 'real', 'text', 'text']
Sample row: ['Massachusetts1', 'John Olver', 'Democratic', 1991.0, 'Re-elected', 'John Olver (D) unopposed']
SQL:

assistant: SELECT "Party" FROM "Table" WHERE "District" = 'Massachusetts4';