def get_highlighted_adjacency_matrix_fig(fig, selected_cells):
    """Add highlights to fig.

    :param fig: See get_adjacency_matrix_fig return value.
    :type fig: plotly.graph_objects.Figure
    :param selected_events: Specified organism_group-organism_group
    relationships inside nested dictionary.
    :type selected_events: dict[str, dict[str, None]]
    :return: Fig with some yellow and transparent rectangles added to
    it.
    :rtype: plotly.graph_objects.Figure
    """
    for organism_group in selected_cells:
        if not len(selected_cells[organism_group]):
            continue
        nested_organism_groups = selected_cells[organism_group]
        for group in nested_organism_groups:
            x = nested_organism_groups[group][0]
            y = nested_organism_groups[group][1]
            fig.add_shape(
                type="rect",
                x0=x-0.5,
                x1=x+0.5,
                y0=y-0.5,
                y1=y+0.5,
                line={
                    "color": "orange",
                    "width": 3
                },
                fillcolor="rgba(240,255,0,0.2)"
            )

    return fig