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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 delete_library_value(self, key: str) -> None: """Delete the library value for the given key. Please consult the developer documentation for a list of valid keys. .. versionadded:: 1.0 Scriptable: Yes """

        desc = Metadata.session_key_map.get(key)
        if desc is not None:
            field_id = desc['path'][-1]
            setattr(ApplicationData.get_session_metadata_model(), field_id, None)
            return
        raise KeyError()