code: def velocity_field():
      Y, X = np.mgrid[-3:3:100j, -3:3:200j]
      U = -1 - X**2 + Y
      V = 1 + X - Y**2
      return X, Y, U, V
  
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 1 for calling a global function with example usage: velocity_field() and returns: X,  Y,  U,  V