Add code for list/array of SE3 poses.

Author: myeatman-bdai

spatialmath/pose3d.py

@@ -1163,7 +1163,10 @@ def inv(self) -> SE3:
             return SE3([smb.trinv(x) for x in self.A], check=False)
 
     def SE2(self) -> SE2:
-        return SE2(self.x, self.y, self.rpy()[2])
+        if len(self) == 1:
+            return SE2(self.x, self.y, self.rpy()[2])
+        else:
+            return SE2([e.SE2() for e in self])
 
     def delta(self, X2: Optional[SE3] = None) -> R6:
         r"""

tests/test_pose3d.py

@@ -667,6 +667,9 @@ def test_functions(self):
         nt.assert_equal(poseSE3.x , poseSE2.x)
         nt.assert_equal(poseSE3.y , poseSE2.y)
 
+        posesSE3 = SE3([poseSE3, poseSE3])
+        posesSE2 = posesSE3.SE2()
+        nt.assert_equal(len(posesSE2), 2)
 
     def test_functions_vect(self):
         # inv