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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 convert_bank_to_hdf(workflow, xmlbank, out_dir, tags=None):
 """Return the template bank in hdf format"""

    if tags is None:
        tags = []
    #FIXME, make me not needed
    if len(xmlbank) > 1:
        raise ValueError('Can only convert a single template bank')

    logging.info('convert template bank to HDF')
    make_analysis_dir(out_dir)
    bank2hdf_exe = PyCBCBank2HDFExecutable(workflow.cp, 'bank2hdf',
                                            ifos=workflow.ifos,
                                            out_dir=out_dir, tags=tags)
    bank2hdf_node = bank2hdf_exe.create_node(xmlbank[0])
    workflow.add_node(bank2hdf_node)
    return bank2hdf_node.output_files