code: def __iter__(self) -> tp.Iterator[str]:
      for name, value in self._mapping.items():
          if isinstance(value, Variable):
              yield name
  
imports: from __future__ import annotations
  import typing
  import jax
  import jax.tree_util
  from flax import traverse_util
  from flax.experimental.nnx.nnx import filterlib, reprlib
  from flax.experimental.nnx.nnx.variables import Variable
label_desc: Use image node_id 7 for calling the StateVariablesMapping obj's underlying member method code with example usage: obj.__iter__() without return types