const defaultValues = ['123','456'];

const field = {                       
                 key: 'testUniqueId',
                 label: 'Contacts,
                 placeholder: "Set value",
                 type: "string",
                 default: defaultValues,
                 choices: [ 
		                   {
			                 "label": "contact one"
                             "value": "123",

                           },
                           {
			                 "label": "contact two"
                             "value": "456",

                           },
		                   {
			                 "label": "contact three"
                             "value": "789",

                            }
		                  ],
                required: true,
                list: true, 
                altersDynamicFields: true
             }                    

I am trying to add multiple values as default in multi-dropdownlist (list is true). But it is binding the default value as complete string.