new_contents: import numpy as np
  import pytest
  
  from sparsereg.model.sindy import *
  
  @pytest.fixture
  def data_linear():
      x = 2 * np.linspace(1, 100, 100).reshape(-1, 1)
      xdot = 2 * np.ones(100).reshape(-1, 1)
      return x, xdot
  
  def test_sindy_derivative(data_linear):
      x, xdot = data_linear
      s = SINDy(dt=1.0).fit(x)
      np.testing.assert_allclose(s.predict(x), xdot)
  
subject: test for sindy