code: private void populatePermissionOverwrites() {
          if (overwrittenUserPermissions == null) {
              overwrittenUserPermissions = new HashMap<>();
              overwrittenUserPermissions.putAll(((ServerChannelImpl) channel).getInternalOverwrittenUserPermissions());
          }
          if (overwrittenRolePermissions == null) {
              overwrittenRolePermissions = new HashMap<>();
              overwrittenRolePermissions.putAll(((ServerChannelImpl) channel).getInternalOverwrittenRolePermissions());
          }
      }
docs: Populates the maps which contain the permission overwrites.