code: def getColCellIdx(self, idx):
      
      c = idx//self.cellsPerColumn
      i = idx - c*self.cellsPerColumn
      return c,i
docs: Get column and cell within column from a global cell index.
      The global index is ``idx = colIdx * nCellsPerCol() + cellIdxInCol``
      
      :param idx: (int) global cell index
      :returns: (tuple) (colIdx, cellIdxInCol)