# Cleanup pairs [String,String]

### Description
Cleanup pairs in `SOURCE`, by e.g. removing self-pairs, symmetrical pairs, etc.
When removing symmetrical pairs, it is unknown which of the two variants (a,b) or (b,a) will be removed.

### Input
- `SOURCE [STRING,STRING]`: a list of string pairs

### Output
- `RESULT [STRING,STRING]`: a list of string pairs