code: def get_phenotype(self, individual_id):
          
          phenotype = 0 # This is if unknown phenotype
          if individual_id in self.individuals:
              phenotype = self.individuals[individual_id].phenotype
          
          return phenotype
docs: Return the phenotype of an individual
          
          If individual does not exist return 0
          
          Arguments:
              individual_id (str): Represents the individual id
          
          Returns:
              int : Integer that represents the phenotype