integers specifying the number of equal-width bins in each
   dimension.
For each N-dimensional point in input:
      * Each of its coordinates is binned independently among the bin
        edges
           corresponding to its dimension
  * Binning results are combined to identify the N-dimensional bin
    (if any)
       into which the point falls

  * If the point falls into a bin, the bin's count (or total
    weight) is incremented

  * Points which do not fall into any bin do not contribute to the
    output

"bins" can be a sequence of N 1D tensors, a sequence of N ints, or
   a single int.
If "bins" is a sequence of N 1D tensors, it explicitly specifies
   the N sequences of bin edges. Each 1D tensor should contain a
   strictly increasing sequence with at least one element. A sequence
   of K bin edges defines K-1 bins, explicitly specifying the left and
   right edges of all bins. Every bin is exclusive of its left edge.