onStart
open fun <T> onStart(name: ConfigurationPropertyName, target: Bindable<T>, context: BindContext): Bindable<T>
Called when binding of an element starts but before any result has been determined.
Return
the actual item that should be used for binding (may be null)
Parameters
<T>
the bindable source type
name
the name of the element being bound
target
the item being bound
context
the bind context