Use autodoc_preserve_defaults = True

See sphinx-doc/sphinx#8771

autodoc_preserve_defaults was new in Sphinx 3.5

Author: peterjc

.travis-tox.ini

@@ -134,7 +134,7 @@ deps =
     rdflib
     reportlab
     scipy
-    sphinx>=1.8.0
+    sphinx>=3.5.0
     numpydoc==1.0.0
     pygments
     sphinx_rtd_theme

Doc/api/conf.py

@@ -19,8 +19,7 @@
 
 # If your documentation needs a minimal Sphinx version, state it here.
 #
-# needs_sphinx = '1.0'
-needs_sphinx = "1.8"
+needs_sphinx = "3.5"
 
 # Add any Sphinx extension module names here, as strings. They can be
 # extensions coming with Sphinx (named 'sphinx.ext.*') or your custom
@@ -110,6 +109,10 @@
     "exclude-members": "__dict__,__weakref__,__module__",
 }
 
+# Experimental feature to preserve the default argument values of
+# functions in source code and keep them not evaluated for readability:
+autodoc_preserve_defaults = True
+
 # To avoid import errors.
 autodoc_mock_imports = ["MySQLdb", "Bio.Restriction.Restriction"]
 if version > "1.77":