input: Write a function to replace all occurrences of a character in a string with the provided replacement character.
  
  def replace_all_occurrences(str, char, replacement):
    return str.replace(char, replacement)
  
  print(replace_all_occurrences("Hello World!", 'l', 'X'))
output: def replace_all_occurrences(str, char, replacement):
    return str.replace(char, replacement)