document and test the in-place changes of datasets

src/toolbox_scs/detectors/hrixs.py

@@ -467,7 +467,7 @@ class hRIXS:
         Example
         -------
 
-            data = h.integrate(data)  # create spectrum by summing pixels
+            h.integrate(data)  # create spectrum by summing pixels
             data.spectrum[0, :].plot()  # plot the spectrum of the first image
         """
         bins = self.Y_RANGE.stop - self.Y_RANGE.start - 20

src/toolbox_scs/test/test_hrixs.py

@@ -16,10 +16,11 @@ class TestHRIXS(unittest.TestCase):
         h.CURVE_A = 0.1
         h.CURVE_B = 0.01
         h.Y_RANGE = slice(30, 170)
-        data = h.integrate(data)
+        r = h.integrate(data)
+        self.assertIs(r, data)
         self.assertEqual(data['spectrum'][1, 50].values[()],
                          28517.704705882352)
         self.assertEqual(data['spectrum'][1, 50].coords['energy'], 90)
 
 if __name__ == "__main__":
-    unittest.main()
+    unittest.main()
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