with Content Or Null
inline fun <T : MessageContent> PossiblySentViaBotCommonMessage<*>.withContentOrNull(): PossiblySentViaBotCommonMessage<T>?
inline fun <T : MessageContent> ChannelContentMessage<*>.withContentOrNull(): ChannelContentMessage<T>?
inline fun <T : MessageContent> PrivateContentMessage<*>.withContentOrNull(): PrivateContentMessage<T>?
inline fun <T : MessageContent> PublicContentMessage<*>.withContentOrNull(): PublicContentMessage<T>?
inline fun <T : MessageContent> FromChannelGroupContentMessage<*>.withContentOrNull(): FromChannelGroupContentMessage<T>?
inline fun <T : MessageContent> AnonymousGroupContentMessage<*>.withContentOrNull(): AnonymousGroupContentMessage<T>?
inline fun <T : MessageContent> CommonGroupContentMessage<*>.withContentOrNull(): CommonGroupContentMessage<T>?