def _ternary_layout(
    title="Ternary contour plot", width=550, height=525, pole_labels=["a", "b", "c"]
):
    """
    Layout of ternary contour plot, to be passed to ``go.FigureWidget``
    object.

    Parameters
    ==========
    title : str or None
        Title of ternary plot
    width : int
        Figure width.
    height : int
        Figure height.
    pole_labels : str, default ['a', 'b', 'c']
        Names of the three poles of the triangle.
    """
    return dict(
        title=title,
        width=width,
        height=height,
        ternary=dict(
            sum=1,
            aaxis=dict(
                title=dict(text=pole_labels[0]), min=0.01, linewidth=2, ticks="outside"
            ),
            baxis=dict(
                title=dict(text=pole_labels[1]), min=0.01, linewidth=2, ticks="outside"
            ),
            caxis=dict(
                title=dict(text=pole_labels[2]), min=0.01, linewidth=2, ticks="outside"
            ),
        ),
        showlegend=False,
    )