def inspect_last(self, stream, only_allocated=False):
        """Return the last value pushed into a stream.

        This function works even if the stream is virtual and no
        virtual walker has been created for it.  It is primarily
        useful to aid in debugging sensor graphs.

        Args:
            stream (DataStream): The stream to inspect.
            only_allocated (bool): Optional parameter to only allow inspection
                of allocated virtual streams.  This is useful for mimicking the
                behavior of an embedded device that does not have a _last_values
                array.

        Returns:
            IOTileReading: The data in the stream

        Raises:
            StreamEmptyError: if there has never been data written to
                the stream.
            UnresolvedIdentifierError: if only_allocated is True and there has not
                been a virtual stream walker allocated to listen to this stream.
        """

        if only_allocated:
            found = False
            for walker in self._virtual_walkers:
                if walker.matches(stream):
                    found = True
                    break

            if not found:
                raise UnresolvedIdentifierError("inspect_last could not find an allocated virtual streamer for the desired stream", stream=stream)

        if stream in self._last_values:
            return self._last_values[stream]

        raise StreamEmptyError(u"inspect_last called on stream that has never been written to", stream=stream)
Return the last value pushed into a stream.

        This function works even if the stream is virtual and no
        virtual walker has been created for it.  It is primarily
        useful to aid in debugging sensor graphs.

        Args:
            stream (DataStream): The stream to inspect.
            only_allocated (bool): Optional parameter to only allow inspection
                of allocated virtual streams.  This is useful for mimicking the
                behavior of an embedded device that does not have a _last_values
                array.

        Returns:
            IOTileReading: The data in the stream

        Raises:
            StreamEmptyError: if there has never been data written to
                the stream.
            UnresolvedIdentifierError: if only_allocated is True and there has not
                been a virtual stream walker allocated to listen to this stream.