You will need to experiment with sending from AN->SV, the final parameter name will depend on the individual nodes. Use your bpy console + autocomplete to find the node names and parameter names. Controlling an SV tree is a very generic manipulation. It's similar to all node trees, native or custom.
tree = bpy.data.node_groups['NodeTree']
tree.nodes['Vectors in'].x_ = 1.6
tree.nodes['Vectors in'].y_ = 1.2