code: def operator(self):
          
          operators = (self.op, self.op + '_', '__' + self.op + '__')
  
          for op in operators:
              if hasattr(self.column, op):
                  return op
  
          raise InvalidFilters("{} has no operator {}".format(self.column.key, self.op))
docs: Get the function operator from his name
  
          :return callable: a callable to make operation on a column