docstr: Test returned properties.
docstr_tok: ["Test","returned","properties","."]
code: def test_properties(self):
      """
      Test returned properties.
      """
      open_interval = (None, None)
      x = [0, 1, 0, 2, 1.5, 0, 3, 0, 5, 9]
      peaks, props = find_peaks(
          x,
          height=open_interval,
          threshold=open_interval,
          prominence=open_interval,
          width=open_interval,
      )
      assert_(len(props) == len(self.property_keys))
      for key in self.property_keys:
          assert_(peaks.size == props[key].size)
  
imports: import copy
  import numpy
  from numpy.testing import assert_, assert_equal, assert_allclose, assert_array_equal
  import pytest
  from pytest import raises, warns
  from scipy.signal._peak_finding import argrelmax, argrelmin, peak_prominences, peak_widths, _unpack_condition_args, find_peaks, find_peaks_cwt, _identify_ridge_lines
  from scipy.signal.windows import gaussian
  from scipy.signal._peak_finding_utils import _local_maxima_1d, PeakPropertyWarning
label_desc: Use image node_id 8 for calling the TestFindPeaks obj's underlying member method code with example usage: obj.test_properties() without return types