code: def validate(self,value):
          '''
          Check for empty values, and for an existing template, but do not check if
          this is one of the initial choices provided.
          '''
          super(ChoiceField,self).validate(value)
  
          try:
              get_template(value)
          except TemplateDoesNotExist:
              raise ValidationError(_('%s is not a valid template.' % value)f validate(self,value):
          '''
          Check for empty values, and for an existing template, but do not check if
          this is one of the initial choices provided.
          '''
          super(ChoiceField,self).validate(value)
  
          try:
              get_template(value)
          except TemplateDoesNotExist:
              raise ValidationError(_('%s is not a valid template.' % value))
docs: Check for empty values, and for an existing template, but do not check if
          this is one of the initial choices provided.