Gets the components for the location

        :param row: track the component is in
        :type row: int
        :param col: the ith member of the track
        :type col: int
        :returns: :class:`AbstractStimulusComponent<sparkle.stim.abstract_component.AbstractStimulusComponent>`

def component(self, row, col):
        """Gets the components for the location

        :param row: track the component is in
        :type row: int
        :param col: the ith member of the track
        :type col: int
        :returns: :class:`AbstractStimulusComponent<sparkle.stim.abstract_component.AbstractStimulusComponent>`
        """
        try:
            comp = self._segments[row][col]
        except:
            # invalid index
            print 'Invalid index'
            return None
        return comp