docs: def dna(self, dna):
          """ 
          Replace this chromosome's DNA with new DNA of equal length,
          assigning the new DNA to the chromosome's genes sequentially.
          
          For example, if a chromosome contains these genes...
            1. 100100
            2. 011011
            
            ...and the new DNA is 111111000000, the genes become:
            1. 111111
            2. 000000
          """
          assert self.length == len(dna)
          i = 0
          
          for gene in self.genes:
              gene.dna = dna[i:i + gene.length]
              
              i += gene.length