class_docstr: Block-Sparse MatMul class; this class handles three types of matrix-multiplication:
     - sparse = dense X dense
     - dense = sparse X dense
     - dense = dense X sparse
  
  For more details about sparsity config, please see `Generative Modeling with Sparse Transformers`: https://arxiv.org/abs/1904.10509
code: def _pad_shape(x, is_sparse):
      max_dim = 3 if is_sparse else 4
      for i in range(max_dim - x.dim()):
          x = x.unsqueeze(0)
      return x
  
imports: import importlib
  import torch
  import triton
  import triton.language
  import triton._C.libtriton
label_desc: Use image node_id 3 for calling the MatMul obj's underlying member method code with example usage: obj._pad_shape(x, is_sparse) and returns: x