Add a docstring-ish for exceptions.relevance.

check-docstring-first has to go unfortunately due to
pre-commit/pre-commit-hooks#159.

Author: Julian

.pre-commit-config.yaml

@@ -5,7 +5,6 @@ repos:
     rev: v4.4.0
     hooks:
       - id: check-ast
-      - id: check-docstring-first
       - id: check-json
       - id: check-toml
       - id: check-vcs-permalinks

jsonschema/exceptions.py

@@ -340,6 +340,15 @@ def relevance(error):
 
 
 relevance = by_relevance()
+"""
+A key function (e.g. to use with `sorted`) which sorts errors by relevance.
+
+Example:
+
+.. code:: python
+
+    sorted(validator.iter_errors(12), key=jsonschema.exceptions.relevance)
+"""
 
 
 def best_match(errors, key=relevance):