input: from typing import List
  
  def replace_all_occurrences(text: str, old_char: str, new_char: str) -> str:
      """ Replace all occurrences of old_char in the given text with the new_char.
      >>> replace_all_occurrences("Hello World!", 'l', 'X')
      'HeXXo WorXd!'
      """
      return text.replace(old_char, new_char)
output:     return text.replace(old_char, new_char)