quadtree.cover(x, y) Expands the quadtree to cover the specified point ⟨x,y⟩, and returns the

quadtree.remove(datum) Removes the specified datum to the quadtree, deriving its coordinates ⟨x,y⟩

quadtree.find(x, y[, radius]) Returns the datum closest to the position ⟨x,y⟩ with the

quadtree.add(datum) Adds the specified datum to the quadtree, deriving its coordinates ⟨x,y⟩

quadtree.size() Returns the total number of data in the quadtree.

quadtree.root() Returns the root node of the quadtree.