[python][feature-request] `GradingPrimary` : fail to assertEqual 2 similar instances

[MrLixm]

Hello, same as in #1641, seems 2 similar ocio.GradingPrimary instance doesn't assert equal.

import unittest

import PyOpenColorIO as ocio


class OcioGradingPrimary(unittest.TestCase):
    def test_equal1(self):

        gp1 = ocio.GradingPrimary(ocio.GRADING_LIN)
        gp1.saturation = 0.3

        gp2 = ocio.GradingPrimary(ocio.GRADING_LIN)
        gp2.saturation = 0.3

        self.assertEqual(gp1, gp2)

    def test_equal2(self):

        gp1 = ocio.GradingPrimary(ocio.GRADING_LOG)
        gp1.contrast = ocio.GradingRGBM(0.5, 0.5, 0.5, 0.0)

        gp2 = ocio.GradingPrimary(ocio.GRADING_LOG)
        gp1.contrast = ocio.GradingRGBM(0.5, 0.5, 0.5, 0.0)

        self.assertEqual(gp1, gp2)


if __name__ == "__main__":
    unittest.main()

CONTEXT: OCIO 2.1.1

I assume it's not an expected behaviour? Cheers. Liam.