docs: def add_individual(self, individual_object):
          """
          Add an individual to the family.
          
          Arguments:
              individual_object (Individual)
              
          """
          ind_id = individual_object.individual_id
          self.logger.info("Adding individual {0}".format(ind_id))
          family_id = individual_object.family
          if family_id != self.family_id:
              raise PedigreeError(self.family, individual_object.individual_id,
                  "Family id of individual is not the same as family id for "\
                                      "Family object!")
          else:
              self.individuals[ind_id] = individual_object
              self.logger.debug("Individual {0} added to family {1}".format(
                  ind_id, family_id
              ))
          return