The contour label (clabel) manual mode fails place any labels. When I click the plot I get an error: 'QuadContourSet' object has no attribute 'ax' and no labels are added. I put the Contour Label Demo ...
to draw the boundary line between True and False regions on a boolean 2d array. Without levels=[.5], one gets the default 8 levels which go at 0, 0.15, 0.3, 0.45, 0.6, 0.75, 0.9, 1.05 resulting in all ...