Issues with occam 2d reading data

[alkirkby]

When I read an occam data file with code below I get an error in Occam2DData

ocd = Occam2DData()
ocd.read_data_file(r'U:\scratch\alisonk\MT\synthetic_data\Forward.fwd')

The problem is line , line 456 :df = df.groupby(["station", "period"]).agg("first")

Really not sure what is going on here!
I have spent quite a bit of time trying to debug but no luck.

I attached the file I am trying to read, it's a forward model from Occam (but have had problems with other files)
Forward.txt

Traceback (most recent call last):

File ~\AppData\Local\miniforge3\envs\mtpy-v2\Lib\site-packages\spyder_kernels\customize\utils.py:209 in exec_encapsulate_locals
exec_fun(compile(code_ast, filename, "exec"), globals)

File occam_resolution_test_setup_inv.py:12
ocd.read_data_file(r'U:\scratch\alisonk\MT\synthetic_data\Forward.fwd')

File C:\git\mtpy-v2\mtpy\modeling\occam2d\data.py:456 in read_data_file
df = df.groupby(["station", "period"]).agg("first")

File ~\AppData\Local\miniforge3\envs\mtpy-v2\Lib\site-packages\pandas\core\groupby\generic.py:1432 in aggregate
result = op.agg()

File ~\AppData\Local\miniforge3\envs\mtpy-v2\Lib\site-packages\pandas\core\apply.py:187 in agg
return self.apply_str()

File ~\AppData\Local\miniforge3\envs\mtpy-v2\Lib\site-packages\pandas\core\apply.py:603 in apply_str
return self._apply_str(obj, func, *self.args, **self.kwargs)

File ~\AppData\Local\miniforge3\envs\mtpy-v2\Lib\site-packages\pandas\core\apply.py:693 in _apply_str
return f(*args, **kwargs)

File ~\AppData\Local\miniforge3\envs\mtpy-v2\Lib\site-packages\pandas\core\groupby\groupby.py:3400 in first
return self._agg_general(

File ~\AppData\Local\miniforge3\envs\mtpy-v2\Lib\site-packages\pandas\core\groupby\groupby.py:1906 in _agg_general
result = self._cython_agg_general(

File ~\AppData\Local\miniforge3\envs\mtpy-v2\Lib\site-packages\pandas\core\groupby\groupby.py:1998 in _cython_agg_general
new_mgr = data.grouped_reduce(array_func)

File ~\AppData\Local\miniforge3\envs\mtpy-v2\Lib\site-packages\pandas\core\internals\managers.py:1473 in grouped_reduce
applied = blk.apply(func)

File ~\AppData\Local\miniforge3\envs\mtpy-v2\Lib\site-packages\pandas\core\internals\blocks.py:393 in apply
result = func(self.values, **kwargs)

File ~\AppData\Local\miniforge3\envs\mtpy-v2\Lib\site-packages\pandas\core\groupby\groupby.py:1973 in array_func
result = self._grouper._cython_operation(

File ~\AppData\Local\miniforge3\envs\mtpy-v2\Lib\site-packages\pandas\core\groupby\ops.py:830 in _cython_operation
return cy_op.cython_operation(

File ~\AppData\Local\miniforge3\envs\mtpy-v2\Lib\site-packages\pandas\core\groupby\ops.py:549 in cython_operation
return self._cython_op_ndim_compat(

File ~\AppData\Local\miniforge3\envs\mtpy-v2\Lib\site-packages\pandas\core\groupby\ops.py:344 in _cython_op_ndim_compat
return self._call_cython_op(

File ~\AppData\Local\miniforge3\envs\mtpy-v2\Lib\site-packages\pandas\core\groupby\ops.py:418 in _call_cython_op
func(

File groupby.pyx:1477 in pandas._libs.groupby.__pyx_fused_cpdef

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