[rr-]

After the first section, Numpydoc read an underlined heading that no section declares as items of the section before it. A lowercase See also after Returns, which numpy itself writes in places, came out as three fake returns:

Returns
-------
inds : tuple of arrays
    The row and column indices.
See also
--------
triu_indices : similar function, for upper-triangular.

Before: returns inds, See also, -------- and triu_indices. Now: the return inds, then a text meta with key see_also, title See also and the section's text as its description.

The rule:

• After the first declared section, an unindented line underlined by as many dashes as it has characters ends the section before it, as a declared title does.
• The heading becomes a text meta. Its key is the title in snake case (Custom Title gives custom_title), and the new DocstringMeta.title keeps the title as written, so compose writes it back and the docstring round-trips.
• Headings inside an Examples section stay in it, since doctest output may hold a table whose header row looks underlined, as in numpy.einsum_path.
• Headings before the first declared section stay in the description, as before.

Matching titles regardless of case, and underlines shorter than the title, are separate changes.

Parity against main: 13 of 29,127 docstrings differ, and each has an undeclared heading after a section.

• 5 corpus cases: See also in numpy.can_cast and numpy.tril_indices, Options in scipy.optimize._minimize_powell, and Methods in two scipy classes.
• 2 new cases.
• 6 generated docstrings. In 2 of them auto-detection now picks Numpydoc over ReST, since Numpydoc reads more of them.
• No stdlib docstring changes.

Bench on 3.8: Numpydoc parse is 1.04x of main, with and without sections, and everything else is 0.98–1.01x.