energy_split_model softening_curve characteristic_length
    coupling_scheme_parameter

    jacobian_factor
    dry_thermal_conductivity
    wet_thermal_conductivity
    dvalue

    add source_term_object
    add flush_stout

    the problem is that files references by an include tag
    in PRJ files may contain content of prj-classes that are
    required to start in OGS6 object. If the included file is not read
    in, but only referenced, the simulation still works as the content
    is in the referenced file but not in the OGS6 object. Here, get_status
    would thrown an error.

    add an active field for include tag
    update active field for prj-classes to handle includes

    add tortuosity and curve to the object
    to generate

    class to represent MSH mesh files

    References for gml, dat, mesh vtu files that are exported to the prj
    file before simulation are standardized to use absolute path. There
    is an option to copy these files into sim_path; file references are
    then made relative.

    When an ogs6_obj is created from a prj file, the prj file may contain
    references to external files. This makes shure file references (gml,
    meshes, dat, py) have absolute paths. Then it is more easy to handle
    file references when sim_path and prj_path differ.