code: def replace(scope, strings, source, dest):
      
      return [s.replace(source[0], dest[0]) for s in strings]
docs: Returns a copy of the given string (or list of strings) in which all
      occurrences of the given source are replaced by the given dest.
  
      :type  strings: string
      :param strings: A string, or a list of strings.
      :type  source: string
      :param source: What to replace.
      :type  dest: string
      :param dest: What to replace it with.
      :rtype:  string
      :return: The resulting string, or list of strings.