Add Node.related many-to-many relationship via nodes_nodes

gargantext/models/nodes.py

@@ -90,6 +90,11 @@ class Node(ValidatorMixin, Base):
     #                            .filter(Node.title_abstract.match('keyword'))
     title_abstract = Column(TSVectorType(regconfig='english'))
 
+    related = relationship('Node',
+                           secondary='nodes_nodes',
+                           primaryjoin='NodeNode.node1_id==Node.id',
+                           secondaryjoin='NodeNode.node2_id==Node.id')
+
     def __new__(cls, *args, **kwargs):
         if cls is Node and kwargs.get('typename'):
             typename = kwargs.pop('typename')