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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 get_metadata(feature_name, etextno):
 """Looks up the value of a meta-data feature for a given text. Arguments: feature_name (str):
 The name of the meta-data to look up. etextno (int):
 The identifier of the Gutenberg text for which to look up the meta-data. Returns: frozenset: The values of the meta-data for the text or an empty set if the text does not have meta-data associated with the feature. Raises: UnsupportedFeature: If there is no MetadataExtractor registered that can extract meta-data for the given feature name. """

    metadata_values = MetadataExtractor.get(feature_name).get_metadata(etextno)
    return frozenset(metadata_values)