def get_phenotype(self, individual_id):
        """
        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
        """
        phenotype = 0 # This is if unknown phenotype
        if individual_id in self.individuals:
            phenotype = self.individuals[individual_id].phenotype
        
        return phenotype