が at the end of the sentence


In the following sentence:

> 切符を買いたいんですが  
>  I would like to buy a ticket.

What is the usage of が?




> _26.4.1.4_ Clause1 **ga**. ( . . . ) in unfinished sentences
>
> Sentences where S2 is left unsaid (implied) are commonly used, especially
> for introducing requests, to test the listener’s reaction, but also to imply
> that realization of S2 is not possible or realistic.
>
> a) ちょっとすみません **が**......。
>
> Chotto sumimasen **ga**......
>
> Excuse me.
>
> b) ちょっとお伺いしたいんです **が** 。
>
> Chotto o-ukagai shitai n desu **ga**.
>
> Could I ask you something?
>
> c) 覚えていないんです **が**......。
>
> Oboete inai n desu **ga**......
>
> I don’t remember.

Source: Japanese: A Comprehensive Grammar. Routledge (2013)

and

<https://itazuraneko.neocities.org/grammar/donnatoki/ngyoudonnatoki.html#%E3%82%93%E3%81%A7%E3%81%99%E3%81%8C>

If you want an explanation in Japanese

