code: def register_yaml():
      
      try:
          import yaml
          registry.register('yaml', yaml.safe_dump, yaml.safe_load,
                            content_type='application/x-yaml',
                            content_encoding='utf-8')
      except ImportError:
  
          def not_available(*args, **kwargs):
              """In case a client receives a yaml message, but yaml
              isn't installed."""
              raise SerializerNotInstalled(
                  "No decoder installed for YAML. Install the PyYAML library")
          registry.register('yaml', None, not_available, 'application/x-yaml')
docs: Register a encoder/decoder for YAML serialization.
  
      It is slower than JSON, but allows for more data types
      to be serialized. Useful if you need to send data such as dates