code: def to_madeline(self):
          
          
          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()
docs: Return a generator with the info in madeline format.
          
          Yields:
              An iterator with family info in madeline format