code: def _prefixed(prefix: str, s: str) -> str:
      """Prefixes a string (if not empty)"""
      return prefix + s if len(s) > 0 else s
  
imports: import unittest
  from typing import Callable, List, Optional, Sequence, Tuple
  import numpy
  from onnx import FunctionProto, GraphProto, ModelProto, NodeProto, SparseTensorProto, TensorProto, ValueInfoProto, checker, compose, helper, parser, version_converter
label_desc: Use image node_id 2 for calling a global function with example usage: _prefixed(prefix, s) and returns: unknown