Add a mesh to the current mesh.  Does not attempt to "join"
        the meshes.

        Parameters
        ----------
        mesh : vtki.PolyData
            The mesh to add.

        inplace : bool, optional
            Updates mesh in-place while returning nothing.

        Returns
        -------
        joinedmesh : vtki.PolyData
            Initial mesh and the new mesh when inplace=False.

def boolean_add(self, mesh, inplace=False):
        """
        Add a mesh to the current mesh.  Does not attempt to "join"
        the meshes.

        Parameters
        ----------
        mesh : vtki.PolyData
            The mesh to add.

        inplace : bool, optional
            Updates mesh in-place while returning nothing.

        Returns
        -------
        joinedmesh : vtki.PolyData
            Initial mesh and the new mesh when inplace=False.

        """
        vtkappend = vtk.vtkAppendPolyData()
        vtkappend.AddInputData(self)
        vtkappend.AddInputData(mesh)
        vtkappend.Update()

        mesh = _get_output(vtkappend)
        if inplace:
            self.overwrite(mesh)
        else:
            return mesh