type_api.py 文件源码

def type_engine(self, dialect):
        """Return a dialect-specific :class:`.TypeEngine` instance
        for this :class:`.TypeDecorator`.

        In most cases this returns a dialect-adapted form of
        the :class:`.TypeEngine` type represented by ``self.impl``.
        Makes usage of :meth:`dialect_impl` but also traverses
        into wrapped :class:`.TypeDecorator` instances.
        Behavior can be customized here by overriding
        :meth:`load_dialect_impl`.

        """
        adapted = dialect.type_descriptor(self)
        if not isinstance(adapted, type(self)):
            return adapted
        elif isinstance(self.impl, TypeDecorator):
            return self.impl.type_engine(dialect)
        else:
            return self.load_dialect_impl(dialect)