sv_tools.py

class AddSVTreeWithSafety(bpy.types.Operator):

    """Tooltip"""
    bl_idname = "node.new_sv_nodetree"
    bl_label = "new sv nodetree with fake user"

    @classmethod
    def poll(cls, context):
        space = context.space_data
        return space.type == 'NODE_EDITOR'

    def execute(self, context):
        """ create new node tree / force fake user to True """
        n = bpy.data.node_groups.new('NodeTree', 'SverchCustomTreeType')
        n.use_fake_user = True
        return {'FINISHED'}


class NODE_HT_header(bpy.types.Header):
    bl_space_type = 'NODE_EDITOR'

    def draw(self, context):
        scene = context.scene
        layout = self.layout
        layout.template_ID(
            data=scene,  # not sure
            property="node_tree",  # not sure
            new="node.new_sv_nodetree")