code: def test_gain_lambda(self):
      samples_in = np.random.normal(0, 1, size=1024).astype(np.float32)
      augmenter = Lambda(
          transform=Gain(min_gain_db=50, max_gain_db=50, p=1.0), p=1.0
      )
      std_in = np.mean(np.abs(samples_in))
      samples_out = augmenter(samples=samples_in, sample_rate=16000)
      std_out = np.mean(np.abs(samples_out))
      assert samples_out.dtype == np.float32
      assert samples_out.shape == samples_in.shape
      assert std_out > 100 * std_in
  
imports: import numpy
  import pytest
  from audiomentations import Lambda, Gain
label_desc: Use image node_id 1 for calling the TestLambda obj's underlying member method code with example usage: obj.test_gain_lambda() without return types