fix pep8

source/_static/code/codons_itertools.py

 from itertools import product
 
+
 def all_codons():
+    """
+    :return: the 64 codons
+    :rtype: list of string
+    """
     alphabet = 'acgt'
-    all_codons = [ ''.join(codon) for codon in product(alphabet, repeat = 3)]
-    return all_codons
\ No newline at end of file
+    all_codons = [''.join(codon) for codon in product(alphabet, repeat=3)]
+    return all_codons