tomlkit 0.15.1 fails on out-of-order table header #632

tomlkit 0.15.1 and earlier fail to parse out-of-order table header. The following example is valid TOML and loads fine with stdlib tomllib.

import tomllib, tomlkit

doc = """\
[a]
b.c = 1
b.d = 2

[x]
y = 1

[a.b.e]
f = 3
"""

tomllib.loads(doc)   # OK
tomlkit.loads(doc)   # ParseError: Key "b" already exists. at line 9 col 0

We noticed this problem while parsing the pyproject.toml file of geventhttpclient-2.5.0 https://github.com/raw/geventhttpclient/geventhttpclient/refs/tags/2.5.0/pyproject.toml . See python-wheel-build/fromager#1356