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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def add_to_dumper(dumper: Type, classes: List[Type]) -> None: """Register user-defined classes with the Dumper. This enables the Dumper to write objects of your classes to a \ YAML file. Note that all the arguments are types, not instances! Args: dumper: Your dumper class(!), derived from yatiml.Dumper classes: One or more classes to add. """

    if not isinstance(classes, list):
        classes = [classes]  # type: ignore
    for class_ in classes:
        if issubclass(class_, enum.Enum):
            dumper.add_representer(class_, EnumRepresenter(class_))
        elif issubclass(class_, str) or issubclass(class_, UserString):
            dumper.add_representer(class_, UserStringRepresenter(class_))
        else:
            dumper.add_representer(class_, Representer(class_))