code: def validate(self, value):
          '''Return a boolean indicating if the value is a valid URI'''
          if self.blank and value == '':
              return True
          if URIValidator.uri_regex.match(value):
              self._choice = value
              return True
          else:
              self.error_message = '%s is not a valid URI' % value
              return Falsf validate(self, value):
          '''Return a boolean indicating if the value is a valid URI'''
          if self.blank and value == '':
              return True
          if URIValidator.uri_regex.match(value):
              self._choice = value
              return True
          else:
              self.error_message = '%s is not a valid URI' % value
              return False
docs: Return a boolean indicating if the value is a valid URI