<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _get_key_from_raw_synset(raw_synset):
 """Derives synset key in the form of `lemma.pos.sense_no` from the provided eurown.py Synset class, Notes ----- Internal function. Do not call directly. Parameters raw_synset : eurown.Synset Synset representation from which lemma, part-of-speech and sense is derived. Returns ------- string Key of the synset in the form of `lemma.pos.sense_no`. """

    pos = raw_synset.pos
    literal = raw_synset.variants[0].literal
    sense = "%02d"%raw_synset.variants[0].sense
    return '.'.join([literal,pos,sense])