code: def matmul(cls, a, b):
      dims = 1
      act_on = -(dims + 1)
      a = a.unsqueeze(-1)
      b = b.unsqueeze(act_on - 1)
      c = cls.times(a, b)
      for d in range(act_on, -1, 1):
          c = cls.sum(c.transpose(-2, -1))
      return c
  
imports: import torch
label_desc: Use image node_id 1 for calling a global function with example usage: matmul(cls, a, b) and returns: c