--- a/docs/conf.py	2020-07-29 11:09:24.036630132 +0100
--- b/docs/conf.py	2020-07-29 11:45:54.186574021 +0100
@@ -119,6 +119,8 @@
         import pyxs
         fn = inspect.getsourcefile(obj)
         fn = os.path.relpath(fn, os.path.dirname(pyxs.__file__))
+        if fn.startswith(".."):
+            return None
         source, lineno = inspect.getsourcelines(obj)
         return fn, lineno, lineno + len(source) - 1