input: Write a function to print out the Pascal's triangle for a given number of rows. The function should accept an integer `n` as its input and print each row of the triangle up to the `n`-th row. If `n` is less than 1, the function should return without printing anything.
  
  def pascal_triangle(n): 
      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
  
  assert pascal_triangle(5)==True
  assert pascal_triangle(0)==False
  assert pascal_triangle(3)==True
  assert pascal_triangle(1)==True
  assert pascal_triangle(7)==True
output: def pascal_triangle(n): 
      if n < 1:
          return
      trow = [1] 
      y = [0] 
      for x in range(n): 
          print(trow) 
          trow=[l+r for l,r in zip(trow + y, y + trow)]