This method does not necessarily use a BioCache but it seems to fit here.

def static_get_pdb_object(pdb_id, bio_cache = None, cache_dir = None):
        '''This method does not necessarily use a BioCache but it seems to fit here.'''
        pdb_id = pdb_id.upper()

        if bio_cache:
            return bio_cache.get_pdb_object(pdb_id)

        if cache_dir:
            # Check to see whether we have a cached copy of the PDB file
            filepath = os.path.join(cache_dir, '{0}.pdb'.format(pdb_id))
            if os.path.exists(filepath):
                return PDB.from_filepath(filepath)

        # Get any missing files from the RCSB and create cached copies if appropriate
        pdb_contents = retrieve_pdb(pdb_id)
        if cache_dir:
            write_file(os.path.join(cache_dir, "%s.pdb" % pdb_id), pdb_contents)
        return PDB(pdb_contents)