code: def test_dense_to_dense():
      todense = DenseTransformer(return_copy=False)
      np.testing.assert_array_equal(X, todense.transform(X))
  
file_path: mlxtend/mlxtend/preprocessing/tests/test_dense_transformer.py
imports: import numpy
  from packaging.version import Version
  from scipy.sparse import issparse
  from sklearn import __version__
  from sklearn.datasets import load_iris
  from sklearn.ensemble import RandomForestClassifier
  from sklearn.feature_extraction.text import TfidfTransformer
  from sklearn.model_selection import GridSearchCV
  from sklearn.pipeline import make_pipeline
  from sklearn.preprocessing import StandardScaler
  from mlxtend.preprocessing import DenseTransformer
label_desc: Use image node_id 1 for calling a global function with example usage: test_dense_to_dense() without return types