OSError: [Errno 22] Invalid argument

[libphy]

If I do

from dmatrix2np import dmatrix_to_numpy
x_test = xgboost.DMatrix(test_data_df)
x_test_np = dmatrix_to_numpy(x_test)

I get

---------------------------------------------------------------------------
OSError                                   Traceback (most recent call last)
/tmp/ipykernel_23836/416855278.py in <module>
      1 from dmatrix2np import dmatrix_to_numpy
      2 
----> 3 x_test_nft_np = dmatrix_to_numpy(x_test_nft)

~/.pyenv/versions/anaconda3-2020.11/lib/python3.8/site-packages/dmatrix2np/dmatrix_to_numpy.py in dmatrix_to_numpy(dmatrix)
     39         with tempfile.NamedTemporaryFile(delete=False) as fp:
     40             dmatrix.save_binary(fp.name)
---> 41             result = stream_parser(fp, dmatrix.num_row(), dmatrix.num_col()).parse()
     42     finally:
     43         # We can safely remove the temp file now, parsing process finished

~/.pyenv/versions/anaconda3-2020.11/lib/python3.8/site-packages/dmatrix2np/dmatrix_v_1_0_0_stream_parser.py in parse(self)
     20         self._parse_magic()
     21         self._parse_version()
---> 22         self._skip_fields()
     23         self._parse_offset_vector()
     24         self._parse_data_vector()

~/.pyenv/versions/anaconda3-2020.11/lib/python3.8/site-packages/dmatrix2np/dmatrix_v_1_0_0_stream_parser.py in _skip_fields(self)
     39         fields_count, = self._read_struct(VECTOR_SIZE_STRUCT)
     40         for _ in range(fields_count):
---> 41             self._skip_field()
     42 
     43     def _skip_field(self):

~/.pyenv/versions/anaconda3-2020.11/lib/python3.8/site-packages/dmatrix2np/dmatrix_v_1_0_0_stream_parser.py in _skip_field(self)
     44         # Skip field name (pascal string)
     45         name_size, = self._read_struct(VECTOR_SIZE_STRUCT)
---> 46         self._handle.seek(name_size, SEEK_CUR)
     47 
     48         # Find field type

~/.pyenv/versions/anaconda3-2020.11/lib/python3.8/tempfile.py in func_wrapper(*args, **kwargs)
    472             @_functools.wraps(func)
    473             def func_wrapper(*args, **kwargs):
--> 474                 return func(*args, **kwargs)
    475             # Avoid closing the file as long as the wrapper is alive,
    476             # see issue #18879.

OSError: [Errno 22] Invalid argument

I'm using xgboost version '1.6.2'. dmatric2np is the latest.