Appends all blocks into a single unstructured grid.

        Parameters
        ----------
        merge_points : bool, optional
            Merge coincidental points.

def combine(self, merge_points=False):
        """Appends all blocks into a single unstructured grid.

        Parameters
        ----------
        merge_points : bool, optional
            Merge coincidental points.

        """
        alg = vtk.vtkAppendFilter()
        for block in self:
            alg.AddInputData(block)
        alg.SetMergePoints(merge_points)
        alg.Update()
        return wrap(alg.GetOutputDataObject(0))