Bidirectional DynamicTableRegion Links Cause `RecursionError` on Read

[h-mayorquin]

When two DynamicTable objects have DynamicTableRegion columns pointing to each other, HDMF encounters infinite recursion when reading the file:

RecursionError: maximum recursion depth exceeded
  File "hdmf/backends/hdf5/h5tools.py", line __read_ref
  File "hdmf/backends/hdf5/h5tools.py", line __read_group
  [... repeats infinitely ...]

Minimal example:

import tempfile
from pathlib import Path

from pynwb import NWBHDF5IO
from pynwb.testing.mock.file import mock_NWBFile
from pynwb.testing.mock.ecephys import mock_ElectrodeTable, mock_Units

nwbfile = mock_NWBFile()
mock_ElectrodeTable(n_rows=3, nwbfile=nwbfile)
mock_Units(num_units=3, nwbfile=nwbfile)

nwbfile.units.add_column(name='electrode_ref', description='Reference to electrodes', data=[0, 1, 2], table=nwbfile.electrodes)
nwbfile.electrodes.add_column(name='unit_ref', description='Reference to units', data=[[i] for i in range(3)], table=nwbfile.units)

with tempfile.TemporaryDirectory() as tmpdir:
    nwb_path = Path(tmpdir) / 'test.nwb'

    with NWBHDF5IO(nwb_path, 'w') as io:
        io.write(nwbfile)

    # This will cause RecursionError
    with NWBHDF5IO(nwb_path, 'r') as io:
        io.read()

Writing actually works it is reading that fails as @rly mentioned.