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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 GetNames(cls):
 """Retrieves the names of the registered artifact definitions. Returns: list[str]: registered artifact definitions names. """

    names = []
    for plugin_class in cls._plugins.values():
      name = getattr(plugin_class, 'ARTIFACT_DEFINITION_NAME', None)
      if name:
        names.append(name)

    return names