Bug: isinstance check fails with Open3D 0.19.0 in test_lidar.py

[Vo1denz]

Problem

Two tests fail with Open3D 0.19.0:

• test_build_point_cloud
• test_view_point_cloud

Error:
TypeError: isinstance() arg 2 must be a type, a tuple of types, or a union

Cause

In Open3D 0.19.0, o3d.geometry.PointCloud is a pybind11_type, not a
standard Python type. isinstance() does not accept pybind11 types.

Fix

Replace isinstance() checks with type(obj).name == "PointCloud"

Environment

• Open3D 0.19.0
• Python 3.11.9
• Windows

[Vo1denz]

After deeper investigation, the root cause is a mock leak from test_yolo.py
that stubs open3d during pytest collection, causing test_lidar.py to receive
a MagicMock instead of the real library.

Fix involves three files:

• tests/conftest.py — pre-caches real open3d before collection
• tests/test_lidar.py — replaces isinstance() with type().name check
• tests/test_yolo.py — minor cleanup

Full suite now passes: 46/46. Opening PR shortly.