input: Write a function to generate the first n elements of the Sierpinski triangle. The function should print a pattern of '1' and '0' characters representing the triangle structure. 
  assert sierpinski_triangle(6)==None
  assert sierpinski_triangle(0)==None
  assert sierpinski_triangle(3)==None
  assert sierpinski_triangle(5)==None
  assert sierpinski_triangle(2)==None
output: def sierpinski_triangle(n):
      if n <= 0:
          return
      triangle = ['1']
      for i in range(1, n):
          new_row = '1'
          for j in range(1, len(triangle[i-1])):
              new_row += str(int(triangle[i-1][j-1]) ^ int(triangle[i-1][j]))
          new_row += '1'
          triangle.append(new_row)
      for row in triangle:
          print(row)