def METHOD_NAME(
        self,
        path: str,
        labels: typing.Optional[typing.Dict] = None,
        *,
        default: typing.Optional[float] = None,
) -> float:
    """
    Returns a single metric value at specified path. If a dict of labels
    is provided, does en exact match of labels (i.e. {} stands for no
    labels; {'a': 'b', 'c': 'd'} matches only {'a': 'b', 'c': 'd'} or
    {'c': 'd', 'a': 'b'} but neither match {'a': 'b'} nor
    {'a': 'b', 'c': 'd', 'e': 'f'}).
    @throws AssertionError if not one metric by path
    """
    entry = self.get(path, set())
    assert (
        entry or default is not None
    ), f'No metrics found by path "{path}"'
    if labels is not None:
        entry = {x for x in entry if x.labels == labels}
        assert (
            entry or default is not None
        ), f'No metrics found by path "{path}" and labels {labels}'
        assert len(entry) <= 1, (
            f'Multiple metrics found by path "{path}" and labels {labels}:'
            f' {entry}'
        )
    else:
        assert (
            len(entry) <= 1
        ), f'Multiple metrics found by path "{path}": {entry}'
    if default is not None and not entry:
        return default
    return next(iter(entry)).value