Some mcmc stacking functions broken in Python 3.11

[bmcguir2]

Attempting to run in Python 3.11 produces the following errors:

`---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
File /Users/Brett/Dropbox/Programs/molsim/ipython_quickstart.py:5
2 sys.path.insert(0, '/Users/Brett/Dropbox/Programs')
4 import numpy as np
----> 5 from molsim.file_handling import load_mol, load_obs, load_multi_obs
6 from molsim.file_io import _write_xy
7 from molsim.constants import ccm, cm, ckm, h, k, kcm

File /Users/Brett/Dropbox/Programs/molsim/molsim/init.py:20
18 from . import analysis
19 from . import mcmc
---> 20 from . import stack

File /Users/Brett/Dropbox/Programs/molsim/molsim/stack.py:118
112 for index in range(4):
113 self._components.append(
114 StackComponent(source_sizes[index], dv, vlsrs[index], tex, ncols[index])
115 )
--> 118 @DataClass
119 class SpectrumChunk:
120 frequency: np.ndarray
121 _intensity: np.ndarray

File ~/miniconda3/lib/python3.11/dataclasses.py:1230, in dataclass(cls, init, repr, eq, order, unsafe_hash, frozen, match_args, kw_only, slots, weakref_slot)
1227 return wrap
1229 # We're called as @DataClass without parens.
-> 1230 return wrap(cls)

File ~/miniconda3/lib/python3.11/dataclasses.py:1220, in dataclass..wrap(cls)
1219 def wrap(cls):
-> 1220 return _process_class(cls, init, repr, eq, order, unsafe_hash,
1221 frozen, match_args, kw_only, slots,
1222 weakref_slot)

File ~/miniconda3/lib/python3.11/dataclasses.py:958, in _process_class(cls, init, repr, eq, order, unsafe_hash, frozen, match_args, kw_only, slots, weakref_slot)
955 kw_only = True
956 else:
957 # Otherwise it's a field of some type.
--> 958 cls_fields.append(_get_field(cls, name, type, kw_only))
960 for f in cls_fields:
961 fields[f.name] = f

File ~/miniconda3/lib/python3.11/dataclasses.py:815, in _get_field(cls, a_name, a_type, default_kw_only)
811 # For real fields, disallow mutable defaults. Use unhashable as a proxy
812 # indicator for mutability. Read the hash attribute from the class,
813 # not the instance.
814 if f._field_type is _FIELD and f.default.class.hash is None:
--> 815 raise ValueError(f'mutable default {type(f.default)} for field '
816 f'{f.name} is not allowed: use default_factory')
818 return f

ValueError: mutable default <class 'numpy.ndarray'> for field _mask is not allowed: use default_factory`

This appears to be a known issue with no resolution that I can find: huggingface/datasets#5230

Downgrading to Python 3.9 works.