Show captured output inside widgets

I’m trying to capture the output of a few objects and then display them inside an HBox.
In the following example, I’m expecting to see the headers printed side by side.

from IPython.display import display_html, DisplayObject
from ipywidgets import HBox, Output
from IPython.utils import capture

class Foo:
    def _ipython_display_(self):
        display_html('<h2>header</h2>', raw=True)

objects = [Foo(), Foo(), Foo()]

with capture.capture_output() as cap:
    for o in objects:

items = []
for captured in cap.outputs:
    out = Output()
    out.append_display_data(DisplayObject(, metadata=captured.metadata))


Actual output in jupyter:

HBox(children=(Output(outputs=({'output_type': 'display_data', 'data': {'text/plain': '<IPython.core.display.D…