def GC_partial(portion):
sequence_count = collections.Counter(portion)<EOL>gc = ((sum([sequence_count[i] for i in '<STR_LIT>']) +<EOL>sum([sequence_count[i] for i in '<STR_LIT>']) / <NUM_LIT> +<EOL><NUM_LIT:2> * sum([sequence_count[i] for i in '<STR_LIT>']) / <NUM_LIT> +<EOL>sum([sequence_count[i] for i in '<STR_LIT>']) / <NUM_LIT>) / len(portion))<EOL>return <NUM_LIT:0> or <NUM_LIT:100> * gc<EOL>
Manually compute GC content percentage in a DNA string, taking
    ambiguous values into account (according to standard IUPAC notation).