Changed typing to Python 3.6 format

docs/source/conf.py

@@ -82,10 +82,7 @@ templates_path = ['_templates']
 # List of patterns, relative to source directory, that match files and
 # directories to ignore when looking for source files.
 # This pattern also affects html_static_path and html_extra_path.
-
-# Disable specific typing until build server supports python 3.9
-# exclude_patterns: list[str] = []
-exclude_patterns = []
+exclude_patterns: List[str] = []
 
 
 # -- Options for HTML output -------------------------------------------------