code: def _compile_marker(self, schema):
          
          # Prepare self
          self.compiled_type = const.COMPILED_TYPE.MARKER
  
          # If this marker is not instantiated -- do it with an identity callable which is valid for everything
          if issubclass(type(schema), six.class_types):
              schema = schema(Identity)  \
                  .on_compiled(name=Identity.name)  # Set a special name on it
  
          # Compile Marker's schema
          key_schema = self.sub_compile(schema.key, matcher=self.matcher)
          schema.on_compiled(key_schema=key_schema, name=key_schema.name)
  
          # Marker is a callable
          self.name = schema.name
          return schema
docs: Compile marker: sub-schema with special type