Global state is another example that leads to fun.

docs/before-you-deprecate.rst

@@ -153,12 +153,20 @@ need or want to clarify:
  * is being able to *raise* exceptions defined by your library part
  of its public API? Or is only catching them considered public.
 
- * a class in your library is defined using `attrs
- <https://www.attrs.org>`_. Is calling `attrs.evolve` directly on
- instances of your class considered public API, and your class is
- thereby permanently coupled to `attrs.evolve`'s public API? Or is
- your use of `attrs` as a library maintainer simply an implementation
- detail?
+ * a class in your library is defined using `attrs`. Is calling
+ `attrs.evolve` directly on instances of your class considered
+ public API, and your class is thereby permanently coupled to
+ `attrs.evolve`'s public API? Or is your use of `attrs` as a
+ library maintainer simply an implementation detail?
+
+ * a function in your library calls `requests.get`, a function which
+ has mutable global state -- it allows someone to import the library
+ and e.g. define `Transport Adapters <requests:transport-adapters>`
+ which, even if done outside your library, affect how it will retrieve
+ the HTTP response. Is your library free to change its HTTP client to
+ another HTTP client even though this will potentially disrupt users
+ who expect their external change to have an affect on your library's
+ behavior?
 
  * ...
 

docs/conf.py

@@ -53,8 +53,9 @@
  "https://python-jsonschema.readthedocs.io/en/latest/",
  None,
  ),
- "packaging": ("https://packaging.python.org/", None),
- "python": ("https://docs.python.org/", None),
+ "packaging": ("https://packaging.python.org/en/latest/", None),
+ "python": ("https://docs.python.org/3/", None),
+ "requests": ("https://requests.readthedocs.io/en/latest/", None),
  "sphinx": ("https://www.sphinx-doc.org/en/master/", None),
 }