Added explicit Overlay and NdOverlay imports in plotting.mpl
@@ -14,6 +14,7 @@ from matplotlib import rc_params_from_file
from ...core import Layout, NdOverlay, Collator, GridMatrix
from ...core.options import Cycle, Palette, Options
+from ...core.overlay import NdOverlay, Overlay
from ...element import * # noqa (API import)
from ..plot import PlotSelector
from .annotation import * # noqa (API import)
