Return True if the value should be pruned; False otherwise.

        If a `table` argument was provided, pass it to filterable_func.

def filter(self, value, table=None):
        '''
        Return True if the value should be pruned; False otherwise.

        If a `table` argument was provided, pass it to filterable_func.
        '''
        if table is not None:
            filterable = self.filterable_func(value, table)
        else:
            filterable = self.filterable_func(value)
        return filterable