code: def to_python(self, value):
          
          value = '' if value in validators.EMPTY_VALUES else smart_text(value)
          if value == self.empty_value or value in validators.EMPTY_VALUES:
              return self.empty_value
          try:
              value = self.coerce(value)
          except (ValueError, TypeError, ValidationError):
              self._on_invalid_value(value)
          return value
docs: Validates that the value is in self.choices and can be coerced to the
          right type.