input: from typing import List
  
  def replace_all_occurrences(str: str, char: str, replacement: str) -> str:
      """ Replaces all occurrences of a given character in a string with the 
      provided replacement character.
  
      >>> replace_all_occurrences("Hello World!", 'l', 'X')
      'HeXXo WorXd!'
      >>> replace_all_occurrences("Python Programming", 'o', 'Z')
      'PyZthn PrZgramming'
      """
output:     result = ""
      for c in str:
          if c == char:
              result += replacement
          else:
              result += c
      return result