docs: def sub_compile(self, schema, path=None, matcher=False):
          """ Compile a sub-schema
  
          :param schema: Validation schema
          :type schema: *
          :param path: Path to this schema, if any
          :type path: list|None
          :param matcher: Compile a matcher?
          :type matcher: bool
          :rtype: CompiledSchema
          """
          return type(self)(
              schema,
              self.path + (path or []),
              None,
              None,
              matcher
          )