Those mapping APIs that allow the map view to be rotated, in the sense of the projected view being rotated around the centre point so that the bearing of the top of the map is not North, usually allow this to be specified either when the map view is created and initialised or later via an exposed property or method.
In the API examples the latter technique is used, to demonstrate that the map view can be dynamically updated in this respect.
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Not applicable: Leaflet.js does not support any bearing other than North.
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