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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 filtered_notebook_metadata(notebook):
 """Notebook metadata, filtered for metadata added by Jupytext itself"""

    metadata = copy(notebook.metadata)
    metadata = filter_metadata(metadata,
                               notebook.metadata.get('jupytext', {}).get('notebook_metadata_filter'),
                               _DEFAULT_NOTEBOOK_METADATA)
    if 'jupytext' in metadata:
        del metadata['jupytext']
    return metadata