user: Question: What are all the metropolis / municipality where mayor is Helen C. De Castro
Columns: ['City / Municipality', 'No. of s Barangay', 'District', 'Area (km²)', 'Population (2010)', 'Income class (2007)', 'ZIP code', 'Mayor']
Types: ['text', 'real', 'real', 'text', 'real', 'text', 'real', 'text']
Sample row: ['Barcelona', 25.0, 2.0, '61.18', 20340.0, '5th', 4712.0, 'Manuel L. Fortes Jr.']
SQL:

assistant: SELECT "City / Municipality" FROM "Table" WHERE "Mayor" = 'Helen C. De Castro';