slightly relax requirement to transitions 0.9.0

requirements.txt

@@ -1,2 +1,2 @@
 tornado>=5.0
-transitions>=0.9.1
+transitions>=0.9.0

sandbox.py

@@ -0,0 +1,48 @@
+from transitions_gui import NestedWebMachine
+from time import sleep
+
+states = [
+    {"name": "PumpON", "states": ["SwitchOFF", "SwitchON"], "initial": "SwitchOFF"},
+    {"name": "PumpOFF", "states": ["SwitchOFF", "SwitchON"], "initial": "SwitchOFF"},
+]
+
+transitions = [
+    ["button_pressed", "PumpON_SwitchOFF", "PumpOFF_SwitchOFF"],
+    ["button_pressed", "PumpON_SwitchON", "PumpOFF_SwitchON"],
+    ["button_pressed", "PumpOFF_SwitchOFF", "PumpON_SwitchOFF"],
+    ["button_pressed", "PumpOFF_SwitchON", "PumpON_SwitchON"],
+    ["button_switched", "PumpON_SwitchOFF", "PumpOFF_SwitchON"],
+    ["button_switched", "PumpON_SwitchON", "PumpOFF_SwitchOFF"],
+    ["switch_toggled", "PumpOFF_SwitchOFF", "PumpON_SwitchON"],
+    ["switch_toggled", "PumpON_SwitchOFF", "PumpOFF_SwitchON"],
+    ["switch_toggled", "PumpOFF_SwitchON", "PumpON_SwitchOFF"],
+    ["switch_toggled", "PumpON_SwitchON", "PumpOFF_SwitchOFF"],
+]
+
+m = NestedWebMachine(states=states, transitions=transitions, auto_transitions=False, initial="PumpOFF",
+                     graph_css=
+                     [
+                        {
+                          "selector": 'edge[source *= "SwitchOFF"][target *= "SwitchON"],'
+                                      'edge[source *= "SwitchON"][target *= "SwitchOFF"]',
+                          "css": {
+                              "label": "",
+                              "source-text-offset": 90,
+                              "source-label": "data(label)",
+                          }
+                        },
+                         {
+                             "selector": "edge",
+                             "css": {
+                                 "font-size": 12
+                             }
+                         }
+                     ]
+                     )
+
+try:
+    while True:
+        sleep(5)
+        m.button_pressed()
+except KeyboardInterrupt:  # Ctrl + C will shutdown the machine
+    m.stop_server()