def METHOD_NAME(self):
    if getattr(self, "_activeModel", None) is None:
        if isinstance(self._staticInput, str):
            # Read from file active cells with 0:air, 1:dynamic, -1 static
            self._activeModel = TensorMesh.read_model_UBC(
                self.mesh, self.basePath + self._staticInput
            )
        else:
            self._activeModel = np.ones(self._mesh.nC)
    return self._activeModel