onal
            Defines the relative heights of the rows. Each row gets a
            relative height of ``height_ratios[i] / sum(height_ratios)``.
            If not given, all rows will have the same height. Equivalent
            to ``gridspec_kw={'height_ratios': [...]}``. In the case of nested
            layouts, this argument applies only to the outer layout.

        subplot_kw : dict, optional
            Dictionary with keywords passed to the `.Figure.add_subplot` call
            used to create each subplot.  These values may be overridden by
            values in *per_subplot_kw*.

        per_subplot_kw : dict, optional
            A dictionary mapping the Axes identifiers or tuples of identifiers
            to a dictionary of keyword arguments to be passed to the
            `.Figure.add_subplot` call used to create each subplot.  The values
            in these dictionaries have precedence over the values in
            *subplot_kw*.

            If *mosaic* is a string, and thus all keys are single characters,
            it is possible to use a single string instead of a tuple as keys;
            i.e. ``"AB"`` is equivalent to ``("A", "B")``.

            .. versionadded:: 3.7

        gridspec_kw : dict, optional
            Dictionary with keywords passed to the `.GridSpec` constructor used
            to create the grid the subplots are placed on. In the case of
            nested layouts, this argument applies only to the outer layout.
            For more complex layouts, users should use `.Figure.subfigures`
            to create the nesting.

        empty_sentinel : object, optional
            Entry in the layout to mean "leave this space empty".  Defaults
            to ``'.'``. Note, if *layout* is a string, it is processed via
            `inspect.cleandoc` to remove leading white space, which may
            interfere with using white-space as the empty sentinel.

        Returns
        -------
        dict[label, Axes]
           A dictionary mapping the labels to the Axes objects.  The order of
           the axes is left-to-right and top-to-bottom of their position in the
           total layout.

        Nr