code: def test_length() -> None:
      u = rcp.Constant(np.array([1, 2, 3, 4, 5, 6, 7]))
      x = u * RandomGaussian()
      assert len(evaluate(x, length=rcp.Length(u))) == 7
  
      l = rcp.Length()
      assert evaluate(l, length=9) == 9
  
file_path: gluonts/test/dataset/artificial/test_recipe.py
imports: import numpy
  import pandas
  import pytest
  import gluonts.dataset.artificial.recipe
  from gluonts.core.component import validated
  from gluonts.core.serde import dump_json, load_json
  from gluonts.dataset.artificial import RecipeDataset
  from gluonts.dataset.artificial.recipe import Add, BinaryMarkovChain, Constant, ConstantVec, Debug, Env, Eval, ForEachCat, Lag, Lifted, LinearTrend, Mul, NanWhere, RandomBinary, RandomCat, RandomGaussian, RandomSymmetricDirichlet, Ref, SmoothSeasonality, Stack, evaluate, generate
  from gluonts.dataset.artificial.recipe import lifted_numpy
  from gluonts.dataset.artificial.recipe import take_as_list
  from gluonts.dataset.common import BasicFeatureInfo, CategoricalFeatureInfo, MetaData
label_desc: Use image node_id 7 for calling a global function with example usage: test_length() without return types