How to use the meshcat.geometry.PngImage.from_file function in meshcat

# field rather than a matrix multiplication.
        scale = geom.float_data[:3]
        element_local_tf[:3, :3] = element_local_tf[:3, :3].dot(np.diag(scale))
        # Attempt to find a texture for the object by looking for an
        # identically-named *.png next to the model.
        # TODO(gizatt): Support .MTLs and prefer them over png, since they're
        # both more expressive and more standard.
        # TODO(gizatt): In the long term, this kind of material information
        # should be gleaned from the SceneGraph constituents themselves, so
        # that we visualize what the simulation is *actually* reasoning about
        # rather than what files happen to be present.
        candidate_texture_path_png = geom.string_data[0:-3] + "png"
        if os.path.exists(candidate_texture_path_png):
            material = meshcat.geometry.MeshLambertMaterial(
                map=meshcat.geometry.ImageTexture(
                    image=meshcat.geometry.PngImage.from_file(
                        candidate_texture_path_png)))
    else:
        print("UNSUPPORTED GEOMETRY TYPE {} IGNORED".format(
              geom.type))
        return meshcat_geom, material

    if material is None:
        def rgb_2_hex(rgb):
            # Turn a list of R,G,B elements (any indexable list
            # of >= 3 elements will work), where each element is
            # specified on range [0., 1.], into the equivalent
            # 24-bit value 0xRRGGBB.
            val = 0
            for i in range(3):
                val += (256**(2 - i)) * int(255 * rgb[i])
            return val