code: def _populate(self, json):
          
          super(InvoiceItem, self)._populate(json)
  
          self.from_date = datetime.strptime(json['from'], DATE_FORMAT)
          self.to_date = datetime.strptime(json['to'], DATE_FORMAT)
docs: Allows population of "from_date" from the returned "from" attribute which
          is a reserved word in python.  Also populates "to_date" to be complete.