code: def ext_q4_matmul(x, q4, q4_width):
      """Matrix multiplication, returns x @ q4"""
      outshape = x.shape[:-1] + (q4_width,)
      x = x.view(-1, x.shape[-1])
      output = torch.empty(
          (x.shape[0], q4_width), dtype=torch.float16, device=x.device
      )
  
      q4_matmul(x, q4, output)
  
      return output.view(outshape)
  
file_path: text-generation-inference/server/text_generation_server/utils/gptq/exllama.py
imports: import torch
  from exllama_kernels import make_q4, q4_matmul, prepare_buffers, set_tuning_params
label_desc: Use image node_id 2 for calling a global function with example usage: ext_q4_matmul(x, q4, q4_width) and returns: output