lxml.html.iterlinks no longer works with bytestrings in lxml 5.1.0

[Chris Warrick]

Python : sys.version_info(major=3, minor=11, micro=7, releaselevel='final', serial=0)
lxml.etree : (5, 1, 0, 0)
libxml used : (2, 12, 3)
libxml compiled : (2, 12, 3)
libxslt used : (1, 1, 39)
libxslt compiled : (1, 1, 39)

Minimum example:

import lxml.html
for link in lxml.html.iterlinks(b'<a href="https://example.com">hello</a>'):
    print(link)

Result with lxml 5.0.1:
(<Element a at 0x7fa4b17fb570>, 'href', 'https://example.com', 0)

Result with lxml 5.1.0:
Traceback (most recent call last):
  File "/tmp/test.py", line 2, in <module>
    for link in lxml.html.iterlinks(b'<a href="https://example.com">hello</a>'):
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "/tmp/lv/lib64/python3.11/site-packages/lxml/html/__init__.py", line 647, in __call__ meth = getattr(doc, self.name)
           ^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'bytes' object has no attribute 'iterlinks'

I suspect this is caused by the replacement of `basestring` with `str` in `_MethodFunc`.
Old: https://github.com/lxml/lxml/blob/3fdcfaa283bdd2b09aff85ceb79f5d4b3e12e392/src/lxml/html/__init__.py#L658
New: https://github.com/lxml/lxml/blob/6133c0e6feeb4714576b8ee3c259dbcad6728e5d/src/lxml/html/__init__.py#L635

Some other files (e.g. src/lxml/html/clean.py) seem to also have this removed and may exhibit this regression.

[scoder (scoder)]

Thanks. This was accidentally lost when modernising the code base after removing Py2 support.
Fixed in https://github.com/lxml/lxml/commit/6619dfd4c446b3a813ab380b22ddd583d32b9a29