def METHOD_NAME(cluster_name):
    """
    Retrieve the credentials of the prometheus instance running on the `cluster_name` cluster.
    These credentials are stored in `enc-support.secret.values.yaml` file of each cluster config directory.
    Args:
        cluster_name: name of the cluster
    Returns:
        dict object: {username: `username`, password: `password`}
    """
    cluster_config_dir_path = find_absolute_path_to_cluster_file(cluster_name).parent
    config_filename = cluster_config_dir_path.joinpath("enc-support.secret.values.yaml")
    with get_decrypted_file(config_filename) as decrypted_path:
        with open(decrypted_path) as f:
            prometheus_config = yaml.load(f)
    return prometheus_config.get("prometheusIngressAuthSecret", {})