def getOverviewLegendType(distance_heatmap_dict):
    """
    Get overview legend types.

    Parameters
    -----------
    distance_heatmap_dict : Dictionary
        Distance Heatmap Dictitonary List formatted for use in visualization. 
    Returns
    --------
    overview_legend_types: List
       Legend types for overview distance matrices
    """
    overview_legend_types = [hd['overview_legend_type'] for hd in distance_heatmap_dict]

    # get unique values in overview_legend_types
    legend_types_unique = set(overview_legend_types)
    overview_legend_types = list(legend_types_unique)

    return overview_legend_types