The first eight measures of this piece contains an expository phrase that is essentially repeated twice. There are some different voice placement the second four measure but the rhythm and chords stay the same. Each phrase ends on a half cadence.
Measures nine through twenty form an asymmetric contrasting period (the rhythm is the same, but the chords are vastly different between the two) that has a half cadence in measure 12 and a PAC in measure 20. The first half of this period is four measures like the opening phrase but the second half of the period is 8 measures long. Having the same downbeat repeated in 15 and 16 helps to mask any feeling of cadence in measure 16. I would say because of the similar rhythm and contour between the first phrase and these two phrases, I would call this a developmental section.
Measures 21 to the end serve as merely as a terminative function. The bass part stays on the A major chord the whole time and there is no significant chordal movement beyond the A major chord in measure 20. I envision this part as being the part where the wanderer exits the stage or screen.