This line is an introduction to a song in the key of "D".
ENDING:Bars 1 & 2 are same as intro. In 3 and 4 the G6 is called Em7 in bar 3 and it leads to a final 5 beat D6.
To 'get out' of the song you cannot finnish the 'troduction' with a 7th so you use a D6/9 or a D major. I like the D6.