code: def _preSynapticTRNCells(self, i, j):
      
      xmin = max(i - 1, 0)
      xmax = min(i + 2, self.trnWidth)
      ymin = max(j - 1, 0)
      ymax = min(j + 2, self.trnHeight)
      trnCells = [
        (x, y) for x in range(xmin, xmax) for y in range(ymin, ymax)
      ]
  
      return trnCells
docs: Given a relay cell at the given coordinate, return a list of the (x,y)
      coordinates of all TRN cells that project to it. This assumes a 3X3 fan-in.
  
      :param i, j: relay cell Coordinates
  
      :return: