code: def _write_expressiontool(step_dir, name, inputs, outputs, expression, parallel):
      
      out_file = os.path.join(step_dir, "%s.cwl" % name)
      out = {"class": "ExpressionTool",
             "cwlVersion": "v1.0",
             "requirements": [{"class": "InlineJavascriptRequirement"}],
             "inputs": [],
             "outputs": [],
             "expression": expression}
      out = _add_inputs_to_tool(inputs, out, parallel)
      out = _add_outputs_to_tool(outputs, out)
      _tool_to_file(out, out_file)
      return os.path.join("steps", os.path.basename(out_file))
docs: Create an ExpressionTool output for the given inputs