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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_release_date(pdb_id):
 """Quick way to get the release date of a PDB ID using the table of results from the REST service Returns None if the release date is not available. Returns: str: Organism of a PDB ID """


    pdb_id = pdb_id.upper()
    if pdb_id not in _property_table().index:
        raise ValueError('PDB ID not in property table')
    else:
        release_date = _property_table().ix[pdb_id, 'releaseDate']
        if pd.isnull(release_date):
            log.debug('{}: no release date available')
            release_date = None

    return release_date