code: def test_fallback_error_no_default(self):
      rngs = nnx.Rngs(some_name=0)
      with pytest.raises(AttributeError, match="No RNG named"):
          key = rngs.dropout()
  
imports: from typing import Any
  import jax
  import jax.numpy
  import pytest
  from flax.experimental import nnx
  from flax.experimental.nnx.nnx.rnglib import _stable_hash
label_desc: Use image node_id 4 for calling the TestRngs obj's underlying member method code with example usage: obj.test_fallback_error_no_default() without return types