code: def decodePolymorphicNucleotide(nuc) :
  	
  	if nuc in polymorphicNucleotides :
  		return polymorphicNucleotides[nuc]
  
  	if nuc in nucleotides :
  		return nuc
  
  	raise ValueError('nuc: %s, is not a valid nucleotide' % nuc)
docs: the opposite of encodePolymorphicNucleotide, from 'R' to ['A', 'G']