class_docstr: Implements the max semiring (max, +, -inf, 0).
  
  Gradients give argmax.
code: def matmul(cls, a, b):
      if has_genbmm and isinstance(a, genbmm.BandedMatrix):
          return b.multiply_max(a.transpose())
      else:
          return matmul(cls, a, b)
  
imports: import torch
label_desc: Use image node_id 1 for calling the MaxSemiring obj's underlying member method code with example usage: obj.matmul(cls, a, b) and returns: b, matmul