code: def topDownCompute(self, topDownIn=None):
      
      output = numpy.zeros(self.numberOfColumns())
      columns = [self.columnForCell(idx) for idx in self.getPredictiveCells()]
      output[columns] = 1
      return output
docs: (From `backtracking_tm.py`)
      Top-down compute - generate expected input given output of the TM
  
      @param topDownIn top down input from the level above us
  
      @returns best estimate of the TM input that would have generated bottomUpOut.