Use proper path separators

This makes the script runnable under Linux/macOS, preventing an OSError

Author: mara004

example_math_nodes.py

@@ -8,6 +8,7 @@
                          update_nodes_by_down,
                          setup_context_menu)
 from example_nodes import Nodes
+from os.path import sep
 
 if __name__ == '__main__':
     QtCore.QCoreApplication.setAttribute(QtCore.Qt.AA_EnableHighDpiScaling)
@@ -46,7 +47,7 @@ def show_nodes_list(node):
     [graph.register_node(n) for n in Nodes]
 
     # load preset session
-    graph.load_session(r'example_nodes\networks\example.nodes')
+    graph.load_session('example_nodes'+sep+'networks'+sep+'example.nodes')
 
     # update nodes
     update_nodes_by_down(graph.all_nodes())