docs: def create_random(cls, length, **kwargs):
          """
          Return a new instance of this gene class with random DNA,
          with characters chosen from ``GENETIC_MATERIAL_OPTIONS``.
          
          length:  the number of characters in the randomized DNA
          **kwargs:  forwarded to the ``cls`` constructor
          """
          dna = ''.join([random.choice(cls.GENETIC_MATERIAL_OPTIONS) for _ in range(length)])
          return cls(dna, **kwargs)