input: from typing import List
  
  
  def replace_all_occurrences(str: str, char: str, replacement: str) -> str:
      """ Replaces all occurrences of a character in a string with the provided replacement character.
      >>> replace_all_occurrences("Hello World!", 'l', 'X')
      'HeXXo WorXd!'
      """
output:     for i in range(len(str)):
          if str[i] == char:
              str = str[:i] + replacement + str[i+1:]
      return str