code: def test_retstep(self):
      for num in [0, 1, 2]:
          for ept in [False, True]:
              y = linspace(0, 1, num, endpoint=ept, retstep=True)
              assert isinstance(y, tuple) and len(y) == 2
              if num == 2:
                  y0_expect = [0.0, 1.0] if ept else [0.0, 0.5]
                  assert_array_equal(y[0], y0_expect)
                  assert_equal(y[1], y0_expect[1])
              elif num == 1 and not ept:
                  assert_array_equal(y[0], [0.0])
                  assert_equal(y[1], 1.0)
              else:
                  assert_array_equal(y[0], [0.0][:num])
                  assert isnan(y[1])
  
imports: import sys
  import pytest
  import numpy
  from numpy import logspace, linspace, geomspace, dtype, array, arange, isnan, ndarray, sqrt, nextafter, stack, errstate
  from numpy._core import sctypes
  from numpy._core.function_base import add_newdoc
  from numpy.testing import assert_, assert_equal, assert_raises, assert_array_equal, assert_allclose, IS_PYPY
label_desc: Use image node_id 13 for calling the TestLinspace obj's underlying member method code with example usage: obj.test_retstep() without return types