input: 
  def replace_all_occurrences(input_string: str, char_to_replace: str, replacement_char: str) -> str:
      """Replace all occurrences of a character in a string with the provided replacement character.
      >>> replace_all_occurrences("Hello World!", 'l', 'X')
      'HeXXo WorXd!'
      >>> replace_all_occurrences("Python Programming", 'o', '0')
      'Pyth0n Pr0gramming'
      """
  
output:     result = ""
      for char in input_string:
          if char == char_to_replace:
              result += replacement_char
          else:
              result += char
      return result