input: Write a python function to remove characters from a string at specified indices.
  assert remove_chars_at_indices("Hello World!", [0, 5, 9]) == "ello orld!"
  assert remove_chars_at_indices("abcdefg", [1, 3, 5]) == "aceg"
  assert remove_chars_at_indices("123456789", [0, 2, 4, 6, 8]) == "2468"
output: def remove_chars_at_indices(s, indices):
      return ''.join([char for i, char in enumerate(s) if i not in indices])