def get_singleton(self):
only_value = None<EOL>for value in six.itervalues(self.ordered_dict):<EOL><INDENT>if only_value is not None:<EOL><INDENT>raise ValueError("<STR_LIT>" % self)<EOL><DEDENT>only_value = value<EOL><DEDENT>if only_value is self.__UnsetSentinel or only_value is None:<EOL><INDENT>raise ValueError("<STR_LIT>" % self)<EOL><DEDENT>return only_value<EOL>
If the row only has one column, return that value; otherwise raise.

        Raises:
            ValueError, if count of columns is not 1.