Karabiner-elements: complex_modifications json error: modifier should be string form: ["any"]

[andybergon]

I am getting the following error

[error] [grabber] complex_modifications json error: modifier should be string form: ["any"]

with the following configuration

{  
   "complex_modifications":{  
      "parameters":{  
         "basic.to_if_alone_timeout_milliseconds":1000
      },
      "rules":[  
         {  
            "manipulators":[  
               {  
                  "description":"Change caps_lock to command+control+option+shift.",
                  "from":{  
                     "key_code":"caps_lock",
                     "modifiers":{  
                        "optional":[  
                           "any"
                        ]
                     }
                  },
                  "to":[  
                     {  
                        "key_code":"left_shift",
                        "modifiers":[  
                           "left_command",
                           "left_control",
                           "left_option"
                        ]
                     }
                  ],
                  "to_if_alone":[  
                     {  
                        "key_code":"escape",
                        "modifiers":{  
                           "optional":[  
                              "any"
                           ]
                        }
                     }
                  ],
                  "type":"basic"
               }
            ]
         }
      ]
   }
}

Is this part that is complaining?

{  
   "key_code":"escape",
   "modifiers":{  
      "optional":[  
         "any"
      ]
   }
}

[tekezo]

                                "to_if_alone": [
                                    {
                                        "key_code": "escape"
                                    }
                                ],