Find all pairs of points whose distance is at most r.
r : positive float
The maximum distance.
p : float, optional
Which Minkowski norm to use. p has to meet the condition
eps : float, optional
Approximate search. Branches of the tree are not explored
if their nearest points are further than r/(1+eps), and
branches are added in bulk if their furthest points are nearer
than r*(1+eps). eps has to be non-negative.
results : set
Set of pairs (i,j), with ``i < j`, for which the corresponding
positions are close.