Scalar left multiplication operators missing from swig python bindings

[scpeters]

We now have swig python bindings for several math classes, such as Vector[234] and Matrix[34]. The c++ classes, such as Matrix3, declare scalar left multiplication operators using friend inline Matrix3<T> operator*(T _s, const Matrix3<T> &_m) (see Matrix3.hh:331-338), but these are not yet included in the python swig bindings, as discussed in #221 (comment).

Desired behavior

We should add bindings for these operators, and confirm it by adding to our tests, such as the following:

diff --git a/src/python/Matrix3_TEST.py b/src/python/Matrix3_TEST.py
index 535e1500..cb50a6b2 100644
--- a/src/python/Matrix3_TEST.py
+++ b/src/python/Matrix3_TEST.py
@@ -123,6 +123,7 @@ class TestMatrix3(unittest.TestCase):
 
         # Scalar
         self.assertAlmostEqual(Matrix3d.ZERO, matrix * 0)
+        self.assertAlmostEqual(Matrix3d.ZERO, 0 * matrix)
 
         # Vector3.ZERO
         self.assertAlmostEqual(Vector3d.ZERO, matrix * Vector3d.ZERO)
@@ -135,6 +136,7 @@ class TestMatrix3(unittest.TestCase):
 
         # scalar 1.0
         self.assertAlmostEqual(matrix, matrix * 1.0)
+        self.assertAlmostEqual(matrix, 1.0 * matrix)
 
         # Vector3.Unit
         # right multiply

Alternatives considered

We could focus on using numpy types instead.

Implementation suggestion

I'm not sure how to implement a friend operator with swig.

Additional context

[azeey]

Can this be closed since we're using pybind11 now?