      &#34;&#34;&#34;
        return self.components

    def get_transmission_by_material(self):
        &#34;&#34;&#34;
        Get the contribution to the transmission by total thickness for each material.

        Layers of the same materials are combined to return one instance with the total thickness.

        Returns
        -------
        `dict`
            Entries are meterials with the total thickness for that material.
        &#34;&#34;&#34;
        material_thickness = dict()
        for name,