cannot debug Errors w/ Openlane Floorplan step w/o enough information, can anyone help on this?

[jiantangATRS]

I created a small example, but floorplan step always errored out.
please help debug what are the root causes?

Thanks

-- some log file --

[INFO]: Running IO Placement (log: designs/fcb_wl_bl/runs/openlane_test/logs/floorplan/4-place_io.log)...
[ERROR]: during executing: "openroad -exit -no_init -python /openlane/scripts/odbpy/io_place.py --config /openlane/designs/fcb_wl_bl/pin_order.cfg --hor-layer met3 --ver-layer met2 --ver-width-mult 2 --hor-width-mult 2 --hor-extension 0 --ver-extension 0 --length 4 --unmatched-error --input-lef /openlane/designs/fcb_wl_bl/runs/openlane_test/tmp/merged.nom.lef --output-def /openlane/designs/fcb_wl_bl/runs/openlane_test/tmp/floorplan/4-io.def --output /openlane/designs/fcb_wl_bl/runs/openlane_test/tmp/floorplan/4-io.odb /openlane/designs/fcb_wl_bl/runs/openlane_test/tmp/floorplan/3-initial_fp.odb |& tee /dev/null /openlane/designs/fcb_wl_bl/runs/openlane_test/logs/floorplan/4-place_io.log"
[ERROR]: Exit code: 1
[ERROR]: Last 10 lines:
File "/nix/store/7hnr99nxrd2aw6lghybqdmkckq60j6l9-python3-3.11.9/lib/python3.11/re/_parser.py", line 989, in parse
p = _parse_sub(source, state, flags & SRE_FLAG_VERBOSE, 0)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/nix/store/7hnr99nxrd2aw6lghybqdmkckq60j6l9-python3-3.11.9/lib/python3.11/re/_parser.py", line 464, in _parse_sub
itemsappend(_parse(source, state, verbose, nested + 1,
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/nix/store/7hnr99nxrd2aw6lghybqdmkckq60j6l9-python3-3.11.9/lib/python3.11/re/_parser.py", line 691, in _parse
raise source.error("nothing to repeat",
re.error: nothing to repeat at position 0
child process exited abnormally

-- designs/fcb_wl_bl/runs/openlane_test/logs/floorplan/4-place_io.log file ---

OpenROAD b16bda7e82721d10566ff7e2b68f1ff0be9f9e38
Features included (+) or not (-): +Charts +GPU +GUI +Python
This program is licensed under the BSD-3 license. See the LICENSE file for details.
Components of this program may be licensed under more restrictive licenses which must be honored.
Top-level design name: fcb_wl_bl
[WARNING]: Using min_distance 0.42 for #N pins to avoid overlap
Traceback (most recent call last):
File "/openlane/scripts/odbpy/io_place.py", line 471, in
io_place()
File "/nix/store/k6rd3zzkbqzahl1bkyypqx8a6i2vg37q-python3-3.11.9-env/lib/python3.11/site-packages/click/core.py", line 1157, in call
return self.main(*args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/nix/store/k6rd3zzkbqzahl1bkyypqx8a6i2vg37q-python3-3.11.9-env/lib/python3.11/site-packages/click/core.py", line 1078, in main
rv = self.invoke(ctx)
^^^^^^^^^^^^^^^^
File "/nix/store/k6rd3zzkbqzahl1bkyypqx8a6i2vg37q-python3-3.11.9-env/lib/python3.11/site-packages/click/core.py", line 1434, in invoke
return ctx.invoke(self.callback, **ctx.params)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/nix/store/k6rd3zzkbqzahl1bkyypqx8a6i2vg37q-python3-3.11.9-env/lib/python3.11/site-packages/click/core.py", line 783, in invoke
return __callback(*args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/openlane/scripts/odbpy/reader.py", line 89, in wrapper
function(**kwargs)
File "/openlane/scripts/odbpy/io_place.py", line 369, in io_place
if re.match(regex, pin_name) is not None:
^^^^^^^^^^^^^^^^^^^^^^^^^
File "/nix/store/7hnr99nxrd2aw6lghybqdmkckq60j6l9-python3-3.11.9/lib/python3.11/re/init.py", line 166, in match
return _compile(pattern, flags).match(string)
^^^^^^^^^^^^^^^^^^^^^^^^
File "/nix/store/7hnr99nxrd2aw6lghybqdmkckq60j6l9-python3-3.11.9/lib/python3.11/re/init.py", line 294, in _compile
p = _compiler.compile(pattern, flags)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/nix/store/7hnr99nxrd2aw6lghybqdmkckq60j6l9-python3-3.11.9/lib/python3.11/re/_compiler.py", line 745, in compile
p = _parser.parse(p, flags)
^^^^^^^^^^^^^^^^^^^^^^^
File "/nix/store/7hnr99nxrd2aw6lghybqdmkckq60j6l9-python3-3.11.9/lib/python3.11/re/_parser.py", line 989, in parse
p = _parse_sub(source, state, flags & SRE_FLAG_VERBOSE, 0)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/nix/store/7hnr99nxrd2aw6lghybqdmkckq60j6l9-python3-3.11.9/lib/python3.11/re/_parser.py", line 464, in _parse_sub
itemsappend(_parse(source, state, verbose, nested + 1,
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/nix/store/7hnr99nxrd2aw6lghybqdmkckq60j6l9-python3-3.11.9/lib/python3.11/re/_parser.py", line 691, in _parse
raise source.error("nothing to repeat",
re.error: nothing to repeat at position 0