user: Question: Which District was the incumbent Julius Kahn from?  Answer:  California 4th district
Columns: ['District', 'Incumbent', 'Party', 'First elected', 'Result', 'Candidates']
Types: ['text', 'text', 'text', 'real', 'text', 'text']
Sample row: ['California 1', 'Clarence F. Lea', 'Democratic', 1916.0, 'Re-elected', 'Clarence F. Lea (D) (unopposed)']
SQL:

assistant: SELECT "District" FROM "Table" WHERE "Incumbent" = 'Julius Kahn';