code: def add_axis(tree: Any, index: int, params: Dict[Any, Any]) -> Any:
      """Add an axis to each AxisMetadata node in a PyTree."""
      return map_axis_meta(lambda x: x.add_axis(index, params), tree)
  
imports: import abc
  import functools
  from typing import Any, Callable, Dict, Generic, Optional, Tuple, TypeVar, Union
  import jax
  from jax.experimental import maps
  from flax import errors, struct
label_desc: Use image node_id 3 for calling a global function with example usage: add_axis(tree, index, params) and returns: map_axis_meta