code: def addCluster(self, cx, cy, item, count, lam_percent=.25):
          
          dx, dy = map(lambda v: v * lam_percent, self.psize)
          total = 0
          while total < count:
              points = np.random.poisson(lam=(dx, dy), size=(count, 2))
              for x, y in points:
                  px, py = (int(x - dx + cx), int(y - dy + cy))
                  if self.getPatch(px, py) is None:
                      self.setPatch(px, py, item)
                      total += 1
                      if total == count:
                          break
docs: Add a Poisson cluster of count items around (x,y).