Add an individual to the family.
        
        Arguments:
            individual_object (Individual)

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