nl: 'Select a valid choice. %(value)s is not one of the available choices.' for 'invalid_choice'. define the method __init__ with 9 arguments: self, choices set to an empty tuple, required set to boolean True, widget set to None,
code: def __init__ ( self , choices = ( ) , required = True , widget = None , label = None , initial = None , help_text = '' , * args , ** kwargs ) :