query("nested.b.isna()") fails

[hombit]

Bug report

We cannot use built-in methods in queries because of an issue in the query parsing code:

from nested_pandas import NestedFrame

nf = NestedFrame.from_flat(NestedFrame({'a': [1, 2], 'b': [3, None]}, index=[1,1]), base_columns=[])
nf.query("nested.b.isna()")

File ~/.virtualenvs/v/lib/python3.12/site-packages/nested_pandas/nestedframe/core.py:357, in NestedFrame.query(self, expr)
    313 """
    314 Query the columns of a NestedFrame with a boolean expression. Specified
    315 queries can target nested columns in addition to the typical column set
   (...)
    353 >>> df.query("mynested.a > 2")
    354 """
    356 # Rebuild queries for each specified nested/base layer
--> 357 exprs_to_use = self._split_query(expr)
    359 # For now (simplicity), limit query to only operating on one layer
    360 if len(exprs_to_use.keys()) != 1:

File ~/.virtualenvs/v/lib/python3.12/site-packages/nested_pandas/nestedframe/core.py:293, in NestedFrame._split_query(self, expr)
    291 expr_slice = split_expr[i].strip("()")
    292 # Check if it's a nested column
--> 293 if self._is_known_hierarchical_column(expr_slice):
    294     nested, colname = split_expr[i].split(".")
    295     current_focus = nested.strip("()")

File ~/.virtualenvs/v/lib/python3.12/site-packages/nested_pandas/nestedframe/core.py:58, in NestedFrame._is_known_hierarchical_column(self, colname)
     56 """Determine whether a string is a known hierarchical column name"""
     57 if "." in colname:
---> 58     left, right = colname.split(".")
     59     if left in self.nested_columns:
     60         return right in self.all_columns[left]

ValueError: too many values to unpack (expected 2)

I believe it is related to #144, but probably would need a different fix

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