http://epydoc.sourceforge.net/api/ - epydoc has great combination of reference documentation combined with codebase visualization. Please note that the two visualisations in "Package epydoc" and "Package Organization" ar both clickable. Once clicked, also feel free to find and click "call graph", which itself visualizes, well, call graph.
Sadly epydoc is no longer maintened and only supports py2. Had an idea of porting it to py3, but never found enough time to do so.
Sadly epydoc is no longer maintened and only supports py2. Had an idea of porting it to py3, but never found enough time to do so.