user: Question: What were the names of the mixed doubles pair for the year that Ralph Nichols played in the men's singles match?
Columns: ['Year', "Men's singles", "Men's doubles", "Women's doubles", 'Mixed doubles']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['1902', 'B. Hamilton', 'W. J. Hamilton B. Hamilton', 'no competition', 'B. Hamilton R. H. Goff']
SQL:

assistant: SELECT "Mixed doubles" FROM "Table" WHERE "Men's singles" = 'Ralph Nichols';