handle python -OO (#2393)

* handle python -OO

* apply black

Author: JohannesBuchner

arviz/plots/backends/__init__.py

@@ -213,10 +213,11 @@ def _copy_docstring(lib, function):
 
 
 # TODO: try copying substitutions too, or autoreplace them ourselves
-output_notebook.__doc__ += "\n\n" + _copy_docstring("bokeh.plotting", "output_notebook").replace(
-    "|save|", "save"
-).replace("|show|", "show")
-output_file.__doc__ += "\n\n" + _copy_docstring("bokeh.plotting", "output_file").replace(
-    "|save|", "save"
-).replace("|show|", "show")
-ColumnDataSource.__doc__ += "\n\n" + _copy_docstring("bokeh.models", "ColumnDataSource")
+if output_notebook.__doc__ is not None:  # if run with python -OO, __doc__ is stripped
+    output_notebook.__doc__ += "\n\n" + _copy_docstring(
+        "bokeh.plotting", "output_notebook"
+    ).replace("|save|", "save").replace("|show|", "show")
+    output_file.__doc__ += "\n\n" + _copy_docstring("bokeh.plotting", "output_file").replace(
+        "|save|", "save"
+    ).replace("|show|", "show")
+    ColumnDataSource.__doc__ += "\n\n" + _copy_docstring("bokeh.models", "ColumnDataSource")