code: def test_linear_constant_intercept():
      x, y, model, params = get_linearmodel(slope=4, intercept=-10)
  
      params["intercept"].vary = False
  
      ret = model.fit(y, params, x=x)
  
      dely = ret.eval_uncertainty(sigma=1)
      slope_stderr = ret.params["slope"].stderr
  
      assert_allclose(dely.min(), 0, rtol=1.0e-2)
      assert_allclose(dely.max(), slope_stderr * x.max(), rtol=1.0e-2)
      assert_allclose(dely.mean(), slope_stderr * x.mean(), rtol=1.0e-2)
  
file_path: lmfit-py/tests/test_model_uncertainties.py
imports: import os
  import numpy
  from numpy.testing import assert_allclose
  from lmfit.lineshapes import gaussian
  from lmfit.models import ExponentialModel, GaussianModel, LinearModel
label_desc: Use image node_id 3 for calling a global function with example usage: test_linear_constant_intercept() without return types