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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 _parse(cls, scope):
 """Parses the input scope into a normalized set of strings. :param scope: A string or tuple containing zero or more scope names. :return: A set of scope name strings, or a tuple with the default scope name. :rtype: set """

    if not scope:
      return ('default',)
    if isinstance(scope, string_types):
      scope = scope.split(' ')
    scope = {str(s).lower() for s in scope if s}
    return scope or ('default',)