Return a generator with the info in madeline format.
        
        Yields:
            An iterator with family info in madeline format

def to_madeline(self):
        """
        Return a generator with the info in madeline format.
        
        Yields:
            An iterator with family info in madeline format
        """
        
        madeline_header = [
            'FamilyID', 
            'IndividualID', 
            'Gender', 
            'Father', 
            'Mother', 
            'Affected',
            'Proband',
            'Consultand',
            'Alive'
        ]
        
        yield '\t'.join(madeline_header)
        
        for family_id in self.families:
            for individual_id in self.families[family_id].individuals:
                individual = self.families[family_id].individuals[individual_id]
                
                yield individual.to_madeline()