def METHOD_NAME():
    """Test that metric key names are converted correctly."""
    metrics = {"1": 1.0, "2": 2.0, "3": 3.0}
    prefix = "foo"
    separator = "."
    converted_metrics = _prefix_metric_keys(metrics, prefix, separator)
    assert converted_metrics == {"foo.1": 1.0, "foo.2": 2.0, "foo.3": 3.0}