sample:
    model:
        origin: guess by J. Stahn
        stack: substrate | film | water
        sub_stacks:
          substrate:
            sequence:
            - material: Si
              roughness: 2
            - material: SiO2
              thickness: 5
              roughness: 3
          film:
            repetitions: 5
            stack: head_group 4 | tail | tail | head_group 4
        layers:
          tail:
            material: tailstuff
            thickness: 22.
        materials:
          head_group:
            sld: 0.2E-06
          tailstuff:
            formula: CH2
            mass_density: 1.2
          SiO2:
            formula: SiO2
            mass_density: 2.5
          Si:
            formula: Si
            mass_density: 2.33
        composits:
          water:
            composition:
              H2O: 0.3
              D2O: 0.7
        globals:
          roughness: {magnitude: 5, unit: angstrom}
          length_unit: angstrom
          mass_density_unit: g/cm^3
          sld_unit: 1/angstrom^2
        reference: ORSO model language | 1.0 | https://www.reflectometry.org/projects/simple_model