def add_condition(self, stream, condition):
self._conditions[condition.name] = (stream, condition)<EOL>return stream<EOL>
Add a condition to a stream.

        Conditions are normally added through :py:meth:`tuple_count`, :py:meth:`contents` or :py:meth:`tuple_check`.

        This allows an additional conditions that are implementations of :py:class:`Condition`.

        Args:
            stream(Stream): Stream to be tested.
            condition(Condition): Arbitrary condition.

        Returns:
            Stream: stream