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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 _allow_custom_expire(self, load):
        '''
        Return bool if requesting user is allowed to set custom expire
        '''
        expire_override = self.opts.get('token_expire_user_override', False)

        if expire_override is True:
            return True

        if isinstance(expire_override, collections.Mapping):
            expire_whitelist = expire_override.get(load['eauth'], [])
            if isinstance(expire_whitelist, collections.Iterable):
                if load.get('username') in expire_whitelist:
                    return True

        return False