$ python t.py
Empty DataFrame
Columns: [_id, qty]
Index: []
pyarrow.Table
_id: int64
qty: double
$ pip install --upgrade pyarrow
Requirement already satisfied: pyarrow in ./venv38-arrow/lib/python3.8/site-packages (3.0.0)
Collecting pyarrow
  Downloading pyarrow-6.0.1-cp38-cp38-macosx_10_13_x86_64.whl (19.1 MB)
...Requirement already satisfied: numpy>=1.16.6 in ./venv38-arrow/lib/python3.8/site-packages (from pyarrow) (1.21.4)
Installing collected packages: pyarrow
  Attempting uninstall: pyarrow
    Found existing installation: pyarrow 3.0.0
    Uninstalling pyarrow-3.0.0:
      Successfully uninstalled pyarrow-3.0.0
ERROR: pip's dependency resolver does not currently take into account all the packages that are installed. This behaviour is the source of the following dependency conflicts.
pymongoarrow 0.1.1 requires pyarrow<3.1,>=3, but you have pyarrow 6.0.1 which is incompatible.
Successfully installed pyarrow-6.0.1
WARNING: You are using pip version 21.0.1; however, version 21.3.1 is available.
You should consider upgrading via the '/Users/shane/tmp/venv38-arrow/bin/python -m pip install --upgrade pip' command.
$ python t.py
Traceback (most recent call last):
  File "t.py", line 1, in <module>
    from pymongoarrow.monkey import patch_all
  File "/Users/shane/tmp/venv38-arrow/lib/python3.8/site-packages/pymongoarrow/__init__.py", line 18, in <module>
    from pymongoarrow.lib import libbson_version
ImportError: dlopen(/Users/shane/tmp/venv38-arrow/lib/python3.8/site-packages/pymongoarrow/lib.cpython-38-darwin.so, 2): Library not loaded: @rpath/libarrow.300.dylib
  Referenced from: /Users/shane/tmp/venv38-arrow/lib/python3.8/site-packages/pymongoarrow/lib.cpython-38-darwin.so
  Reason: image not found