code: def _cast_field(self, cast_to, value):
          
          if cast_to in (int, long, str):
              return cast_to(value)
          elif cast_to == unicode:
              try:
                  value = value.decode(self.charset, self.errors)
              except UnicodeEncodeError, e:
                  raise InvalidData("Error encoding unicode value '%s': %s" % (repr(value), e))
  
              return value
          elif cast_to in (any, bytes):
              return value
          else:
              raise TypeError("Invalid field type %s" % (cast_to))
docs: Convert field type from raw bytes to native python type
  
          :param cast_to: native python type to cast to
          :type cast_to: a type object (one of bytes, int, unicode (str for py3k))
          :param value: raw value from the database
          :type value: bytes
  
          :return: converted value
          :rtype: value of native python type (one of bytes, int, unicode (str for py3k))