docs: add model-container py example

Author: mwfarb

content/python/attributes/model_container.md

@@ -0,0 +1,40 @@
+---
+title: ModelContainer
+layout: default
+parent: Attributes
+grand_parent: Python Library
+---
+
+# Model Container
+
+Overrides absolute size for a 3D model. The model can be a glTF, glb, obj, or any other supported format. The model will be rescaled to fit to the sizes specified for each axes.
+
+This example scales the Duck model into a 10 x 10 x 10 box.
+
+`arena-py` API Reference for [ModelContainer](/content/python-api/attributes/model_container).
+
+```python
+from arena import *
+
+scene = Scene(host="arenaxr.org", scene="example")
+
+model_container = ModelContainer(
+    x=10,
+    y=10,
+    z=10,
+)
+
+@scene.run_once
+def make_model_container():
+    scene.add_object(
+        GltfModel(
+            object_id="gltf-model-duck",
+            url="store/models/Duck.glb",
+            position=(0, 1, -5),
+            model_container=model_container,
+            persist=True,
+        )
+    )
+
+scene.run_tasks()
+```