code: def getSegmentOnCell(self, c, i, segIdx):
      
      return self.cells[c][i][segIdx]
docs: Return the segment on cell (c,i) with index sidx.
      Returns the segment as following list:
        [  [segmentID, sequenceSegmentFlag, frequency],
           [col1, idx1, perm1],
           [col2, idx2, perm2], ...
        ]