def dissolve_contiguous(input_gdf):
    """Dissolve geometries into one polygon then explode to ensure no multiparts.
    Args:
        input_gdf (geopandas.GeoDataFrame): Geodataframe with polygon geometry column.
    Returns:
        geopandas.GeoDataFrame: Polygon geodataframe with cleaned internal boundaries.
    """
    input_gdf["diss"] = 1
    input_gdf = input_gdf.dissolve(by="diss", as_index=False)
    input_gdf = input_gdf.explode(index_parts=True)
    return input_gdf