NestedFrame.drop(columns=["nested.t"]) doesn't work

[hombit]

Bug report

It looks like only nf.drop(labels=..., axis=1) is supported for nested columns, not nf.drop(columns=...), which is confusing:

from nested_pandas.datasets import generate_data

nf = generate_data(3, 2)
nf.drop(labels="a", axis=1)  # works
nf.drop(columns="a")  # works
nf.drop(labels="nested.t", axis=1)  # works
nf.drop(columns="nested.t")  # fails

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