func_code: def overlap(x1=0, y1=0, r1=1, x2=0, y2=0, r2=1):
      d = ((x2 - x1) ** 2 + (y2 - y1) ** 2) ** 0.5
      rpos = r1 + r2 - 1
      rneg = r1 - r2
      if d == rpos:
          return True
      elif d == rneg:
          return True
      else:
          return False