The ZODB is a mature graph database written in Python and optimized in C. Just subclass off of class Persistent Object, and Persistent Container, and your objects, graphs and applications become persistent.
The market for Graph Databases has recently exploded, as evidenced by over $200Million invested in graph database companies. Most of the graph databases are written in Java.
If you are a Python developer, you will find much greater productivity using a graph database written in Python, than one written in statically bound Java. The major Java databases constrain you to one of several persistent data types. Persistent Python, supported by the ZODB allows you to make any Python data structure persistent.
The new ZODB Demo makes it very easy to start building your own applications on top of the ZODB. You can start by customizing the TreeLeaf, TreeBranch and TreeRoot classes and their templates. You get CRUD for free.
The demo includes traditional relational CRUD, Create, Read, Update, and Delete. But it also includes the extended graph CRUD. Rename a Leaf or Branch. Cut and paste leaves or branches, copy and paste leaves or branches. The talk also demonstrates the soon-to-be released view historic versions and restore a previous version.