Always set 'mesh' and 'input' properties as str. Refactor input concatenation

        Parameters

        ----------

        input : str or pathlib.Path object

        input : str object

            Griffin input file

        mesh : str or pathlib.Path object

        mesh : str object

            Location of the griffin mesh (either input or exodus)

        cwd : str or  pathlib.Path object

            Directory from which to run Griffin

        return p.returncode

    def report_materials(self):

        """

        Prints materials assigned and available ISOXML isotopes to screen

        """

        mesh_materials = self.get_material_assignments()

        mat_str = "Materials applied in the Griffin mesh:\n"

        for material, isotopes in mesh_materials.items():

        return invalid_mats, unused_mats

    def get_material_assignments(self):

        """

        Concatenate all MOOSE inputs and

        """

        # open the mesh and options files

        lines = []

        with open(self.input, 'r') as input:

            lines += input.readlines()

        with open(self.mesh, 'r') as mesh:

            lines += mesh.readlines()

        for file in (self.input, self.mesh):

            if file.endswith('.i'):

                with open(file, 'r') as fh:

                    lines += fh.readlines()

        return parse_moose_materials(lines)

    @input.setter

    def input(self, input):

        cv.check_type('Griffin input', input, (str, Path))

        self._input = Path(input).absolute()

        self._input = str(Path(input).absolute())

    @property

    def mesh(self):

    @mesh.setter

    def mesh(self, mesh):

        cv.check_type('Griffin mesh', mesh, (str, Path))

        self._mesh = mesh

        self._mesh = str(mesh)

    @property

    def xs(self):