Loads client configurations from a YAML file.

    :param filename: YAML file name.
    :type filename: unicode | str
    :param configuration_class: Class of the configuration object to create.
    :type configuration_class: class
    :return: A dictionary of client configuration objects.
    :rtype: dict[unicode | str, dockermap.map.config.client.ClientConfiguration]

def load_clients_file(filename, configuration_class=ClientConfiguration):
    """
    Loads client configurations from a YAML file.

    :param filename: YAML file name.
    :type filename: unicode | str
    :param configuration_class: Class of the configuration object to create.
    :type configuration_class: class
    :return: A dictionary of client configuration objects.
    :rtype: dict[unicode | str, dockermap.map.config.client.ClientConfiguration]
    """
    with open(filename, 'r') as f:
        return load_clients(f, configuration_class=configuration_class)