Resolved wwt.*ground trait metadata errors

pywwt/core.py

@@ -392,7 +392,7 @@ class BaseWWTWidget(HasTraits):
         return sorted(self._available_layers)
 
     foreground = Unicode('Digitized Sky Survey (Color)',
-                         help='The layer to show in the foreground (`str`)').tag(wwt_reset=True)
+                         help='The layer to show in the foreground (`str`)').tag(wwt=None, wwt_reset=True)
 
     @observe('foreground')
     def _on_foreground_change(self, changed):
@@ -409,7 +409,7 @@ class BaseWWTWidget(HasTraits):
             raise TraitError('foreground is not one of the available layers')
 
     background = Unicode('Hydrogen Alpha Full Sky Map',
-                         help='The layer to show in the background (`str`)').tag(wwt_reset=True)
+                         help='The layer to show in the background (`str`)').tag(wwt=None, wwt_reset=True)
 
     @observe('background')
     def _on_background_change(self, changed):
@@ -426,7 +426,8 @@ class BaseWWTWidget(HasTraits):
             raise TraitError('background is not one of the available layers')
 
     foreground_opacity = Float(0.8, help='The opacity of the foreground layer '
-                                         '(`float`)').tag(wwt_reset=True)
+                                         '(`float`)').tag(wwt=None,
+                                                          wwt_reset=True)
 
     @observe('foreground_opacity')
     def _on_foreground_opacity_change(self, changed):