def METHOD_NAME(self, request):
    """Given a tag and list of runs, return dict of ScalarEvent arrays."""
    if request.method != "POST":
        raise werkzeug.exceptions.MethodNotAllowed(["POST"])
    tags = request.form.getlist("tag")
    runs = request.form.getlist("runs")
    if len(tags) != 1:
        raise errors.InvalidArgumentError(
            "tag must be specified exactly once"
        )
    tag = tags[0]
    ctx = plugin_util.context(request.environ)
    experiment = plugin_util.experiment_id(request.environ)
    (body, mime_type) = self.scalars_multirun_impl(
        ctx, tag, runs, experiment
    )
    return http_util.Respond(request, body, mime_type)