<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def custom_resolve(self):
 """ If a custom resolver is defined, perform custom resolution on the contained addresses. :return: """

        if not callable(self.custom_resolver):
            return
        new_addresses = []
        for address in self.addresses:
            for new_address in self.custom_resolver(address):
                new_addresses.append(new_address)
        self.addresses = new_addresses