&Heatmap implements IntoIterator but it does not have an iter method. This is somewhat confusing since in most cases where a type &T implements IntoIteratorT also has an iter method that does the same thing. All this PR does is address this missing method.
&HeatmapimplementsIntoIteratorbut it does not have anitermethod. This is somewhat confusing since in most cases where a type&TimplementsIntoIteratorTalso has anitermethod that does the same thing. All this PR does is address this missing method.