code: def component(self, row, col):
          
          try:
              comp = self._segments[row][col]
          except:
              # invalid index
              print 'Invalid index'
              return None
          return comp
docs: 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>`