def get_payer_channel(channelidentifiers_to_channels, transfer_pair):
    """ Returns the payer channel of a given transfer pair. """
    payer_channel_identifier = transfer_pair.payer_transfer.balance_proof.channel_address
    assert payer_channel_identifier in channelidentifiers_to_channels
    payer_channel = channelidentifiers_to_channels[payer_channel_identifier]

    return payer_channel