code: def test_startpoints():
      X, Y, U, V = velocity_field()
      start_x, start_y = np.meshgrid(
          np.linspace(X.min(), X.max(), 5),
          np.linspace(Y.min(), Y.max(), 5),
      )
      start_points = np.column_stack([start_x.ravel(), start_y.ravel()])
      plt.streamplot(X, Y, U, V, start_points=start_points)
      plt.plot(start_x, start_y, "ok")
  
file_path: matplotlib/lib/matplotlib/tests/test_streamplot.py
imports: import numpy
  from numpy.testing import assert_array_almost_equal
  import pytest
  import matplotlib.pyplot
  from matplotlib.testing.decorators import image_comparison
  import matplotlib.transforms
label_desc: Use image node_id 3 for calling a global function with example usage: test_startpoints() without return types