Applies any defined transformation to the given value

def _transform(self, value):
        """ Applies any defined transformation to the given value
        """
        if self.transform:
            try:
                value = self.transform(value)
            except:
                import sys
                exc_type, exc_obj, exc_tb = sys.exc_info()
                raise AssertionError('Error applying transformation <{0}>: {2}: {3}'.format(
                    self.transform.__name__, value, exc_type.__name__, exc_obj))

        return value