input: def pascal_triangle(n: int) -> None:
      """Print out Pascal's triangle for a given number of rows.
      >>> pascal_triangle(5)
      [1]
      [1, 1]
      [1, 2, 1]
      [1, 3, 3, 1]
      [1, 4, 6, 4, 1]
      """
      trow = [1] 
      y = [0] 
      for x in range(max(n, 0)): 
          print(trow) 
          trow=[l+r for l,r in zip(trow + y, y + trow)] 
      return n>=1
output:     
      trow = [1] 
      y = [0] 
      for x in range(max(n, 0)): 
          print(trow) 
          trow=[l+r for l,r in zip(trow + y, y + trow)] 
      return n>=1
  