human
Solve the following python programming problem given the following code:
def _extract_field(sql_attr) : 
    def extract_field_formatter(translator, expr) : 
        op = expr.op () 
        arg = translator.translate (op.args [0]) 
        return "extract({0!s}, '{1!s}')".format (arg, sql_attr) 
return <MASK> 
    
    Given the code above, what is a proper replacement for <MASK>?
assistant
#Here is a proper replacement for <MASK>.
def extract_field_formatter(