def _depgrep_node_label_use_action(_s, _l, tokens):
    """
    Returns the node label used to begin a tgrep_expr_labeled.  See
    `_depgrep_segmented_pattern_action`.

    Called for expressions like (`tgrep_node_label_use`)::

        =s

    when they appear as the first element of a `tgrep_expr_labeled`
    expression (see `_depgrep_segmented_pattern_action`).

    It returns the node label.
    """
    assert len(tokens) == 1
    assert tokens[0].startswith('=')
    return tokens[0][1:]
