code: def set_object_metadata(self, container, obj, metadata, clear=False,
              extra_info=None, prefix=None):
          
          return container.set_object_metadata(obj, metadata, clear=clear,
                  prefix=prefix)
docs: Accepts a dictionary of metadata key/value pairs and updates the
          specified object metadata with them.
  
          If 'clear' is True, any existing metadata is deleted and only the
          passed metadata is retained. Otherwise, the values passed here update
          the object's metadata.
  
          'extra_info; is an optional dictionary which will be populated with
          'status', 'reason', and 'headers' keys from the underlying swiftclient
          call.
  
          By default, the standard object metadata prefix ('X-Object-Meta-') is
          prepended to the header name if it isn't present. For non-standard
          headers, you must include a non-None prefix, such as an empty string.