user: Question: how many people wrote the episode directed by Rob Schrab?
Columns: ['Series no.', 'Season no.', 'Title', 'Directed by', 'Written by', 'Original air date', 'Production code']
Types: ['real', 'real', 'text', 'text', 'text', 'text', 'real']
Sample row: [6.0, 1.0, '"I See Her Face Everywhere"', 'Matt Shakman', 'Rob Corddry', 'August22,2010', 201.0]
SQL:

assistant: SELECT "Written by" FROM "Table" WHERE "Directed by" = 'Rob Schrab';