Adjust for pandas 2.1

[khaeru]

At iiasa/message-ix-models#117, some tests are failing with:

Traceback

>       assert (
            expected == qty_out.sel(node_loc=node_loc, technology="coal_ppl", year=2022)
        ).all()

message_ix_models/tests/util/test_node.py:106: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
../../genno/genno/core/attrseries.py:455: in sel
    data = data.droplevel(list(to_drop & set(data.index.names)))
../../../.venv/3.11/lib/python3.11/site-packages/pandas/core/generic.py:898: in droplevel
    return self.set_axis(new_labels, axis=axis, copy=None)
../../../.venv/3.11/lib/python3.11/site-packages/pandas/core/series.py:4962: in set_axis
    return super().set_axis(labels, axis=axis, copy=copy)
../../../.venv/3.11/lib/python3.11/site-packages/pandas/core/generic.py:745: in set_axis
    return self._set_axis_nocheck(labels, axis, inplace=False, copy=copy)
../../../.venv/3.11/lib/python3.11/site-packages/pandas/core/generic.py:756: in _set_axis_nocheck
    obj = self.copy(deep=copy and not using_copy_on_write())
../../../.venv/3.11/lib/python3.11/site-packages/pandas/core/generic.py:6685: in copy
    return self._constructor_from_mgr(data, axes=data.axes).__finalize__(
../../../.venv/3.11/lib/python3.11/site-packages/pandas/core/series.py:589: in _constructor_from_mgr
    return self._constructor(ser, copy=False)
../../genno/genno/core/attrseries.py:130: in __init__
    data, name = Quantity._single_column_df(data, name, copy=kwargs.get("copy"))
../../genno/genno/core/quantity.py:102: in _single_column_df
    data.set_axis(pd.MultiIndex.from_product([data.index]), copy=copy),
../../../.venv/3.11/lib/python3.11/site-packages/pandas/core/arrays/categorical.py:449: in __init__
    codes, categories = factorize(values, sort=True)
../../../.venv/3.11/lib/python3.11/site-packages/pandas/core/algorithms.py:763: in factorize
    return values.factorize(sort=sort, use_na_sentinel=use_na_sentinel)
../../../.venv/3.11/lib/python3.11/site-packages/pandas/core/base.py:1195: in factorize
    codes, uniques = algorithms.factorize(
../../../.venv/3.11/lib/python3.11/site-packages/pandas/core/algorithms.py:795: in factorize
    codes, uniques = factorize_array(
../../../.venv/3.11/lib/python3.11/site-packages/pandas/core/algorithms.py:592: in factorize_array
    hash_klass, values = _get_hashtable_algo(values)
../../../.venv/3.11/lib/python3.11/site-packages/pandas/core/algorithms.py:273: in _get_hashtable_algo
    values = _ensure_data(values)
../../../.venv/3.11/lib/python3.11/site-packages/pandas/core/algorithms.py:150: in _ensure_data
    elif is_bool_dtype(values.dtype):
../../../.venv/3.11/lib/python3.11/site-packages/pandas/core/dtypes/common.py:1235: in is_bool_dtype
    if isinstance(arr_or_dtype, ABCIndex):
../../../.venv/3.11/lib/python3.11/site-packages/pandas/core/dtypes/generic.py:44: in _instancecheck
    return _check(inst) and not isinstance(inst, type)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

inst = dtype('int64')

    def _check(inst) -> bool:
>       return getattr(inst, attr, "_typ") in comp
E       RecursionError: maximum recursion depth exceeded while calling a Python object

This occurs with pandas 2.1 (released today) but not pandas < 2.1. Additionally, it is was not triggered by the genno test suite—but only because no workflow run had occurred with the 2.1.0 release.

PR checklist

• Add a test that reproduces the exception.
• Checks all ✅
• Update documentation N/A, internals only.
• Update doc/whatsnew.rst

[khaeru]

The test runs also give the following new warnings:

genno/tests/test_computations.py::test_aggregate[attrseries-True]
  /opt/hostedtoolcache/Python/3.11.4/x64/lib/python3.11/site-packages/xarray/core/dataarray.py:885: FutureWarning: elementwise comparison failed; returning scalar instead, but in the future will perform elementwise comparison
    return key in self.data

genno/tests/test_util.py::test_parse_units0[['kg', 'kg']-'kg']
genno/tests/test_util.py::test_parse_units0[['foo/bar']-'foo/bar']
genno/tests/test_util.py::test_parse_units0[[]-'dimensionless']
genno/tests/test_util.py::test_parse_units1
  /home/runner/work/genno/genno/genno/util.py:98: FutureWarning: unique with argument that is not not a Series, Index, ExtensionArray, or np.ndarray is deprecated and will raise in a future version.
    unit = pd.unique(data)

genno/tests/compat/test_pyam.py: 12 warnings
  /opt/hostedtoolcache/Python/3.11.4/x64/lib/python3.11/site-packages/pyam/core.py:2691: FutureWarning: unique with argument that is not not a Series, Index, ExtensionArray, or np.ndarray is deprecated and will raise in a future version.
    index = pd.unique(index)

genno/tests/core/test_quantity.py::TestQuantity::test_bfill[attrseries]
genno/tests/core/test_quantity.py::TestQuantity::test_bfill[attrseries]
  /home/runner/work/genno/genno/genno/core/attrseries.py:189: FutureWarning: DataFrame.fillna with 'method' is deprecated and will raise in a future version. Use obj.ffill() or obj.bfill() instead.
    .fillna(method="bfill", axis=1, limit=limit)

genno/tests/core/test_quantity.py::TestQuantity::test_ffill[attrseries]
genno/tests/core/test_quantity.py::TestQuantity::test_ffill[attrseries]
  /home/runner/work/genno/genno/genno/core/attrseries.py:274: FutureWarning: DataFrame.fillna with 'method' is deprecated and will raise in a future version. Use obj.ffill() or obj.bfill() instead.
    .fillna(method="ffill", axis=1, limit=limit)

[codecov-commenter]

Codecov Report

Merging #99 (fdef63e) into main (bdead68) will not change coverage.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff            @@
##              main       #99   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           45        45           
  Lines         3819      3823    +4     
=========================================
+ Hits          3819      3823    +4     

Files Changed	Coverage Δ
genno/core/quantity.py	100.00% <ø> (ø)
genno/tests/core/test_quantity.py	100.00% <ø> (ø)
genno/tests/test_computations.py	100.00% <ø> (ø)
genno/core/attrseries.py	100.00% <100.00%> (ø)
genno/tests/compat/test_pyam.py	100.00% <100.00%> (ø)
genno/util.py	100.00% <100.00%> (ø)