new_contents: import numpy as np
  import pyfds as fds
  
  
  def test_output():
      out = fds.Output(fds.LineRegion([0, 1, 2], [0, 0.2], 'test output'))
      out.signals = [np.linspace(0, 1) for _ in range(len(out.region.indices))]
      assert np.allclose(out.mean_signal, np.linspace(0, 1))
  
subject: Add test case for Output class.