input: Write a Python function to convert a pascal triangle to a 2D list.
  assert pascal_to_list("1\n1 1\n1 2 1\n1 3 3 1\n1 4 6 4 1") == [[1], [1, 1], [1, 2, 1], [1, 3, 3, 1], [1, 4, 6, 4, 1]]
  assert pascal_to_list("1\n1 1\n1 2 1") == [[1], [1, 1], [1, 2, 1]]
  assert pascal_to_list("1\n1 1") == [[1], [1, 1]]
output: def pascal_to_list(pascal_str):
      return [[int(num) for num in line.split()] for line in pascal_str.split('\n')]