code: def _parse_bool_default_value(property_name, default_value_string):
      
      lowercased_value_string = default_value_string.lower()
      if lowercased_value_string in {'0', 'false'}:
          return False
      elif lowercased_value_string in {'1', 'true'}:
          return True
      else:
          raise AssertionError(u'Unsupported default value for boolean property "{}": '
                               u'{}'.format(property_name, default_value_string))
docs: Parse and return the default value for a boolean property.