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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 register():
    '''Register the plugin only if required signals are available'''
    for sig_name in _SIGNAL_HANDLERS_DB.keys():
        if not hasattr(signals, sig_name):
            _LOGGER.error((
                'The i18n_subsites plugin requires the {} '
                'signal available for sure in Pelican 3.4.0 and later, '
                'plugin will not be used.').format(sig_name))
            return

    for sig_name, handler in _SIGNAL_HANDLERS_DB.items():
        sig = getattr(signals, sig_name)
        sig.connect(handler)