code: def change_password(self, user, password, send_email=None):
          
          user.password = password
          self.user_manager.save(user)
          if send_email or (app.config.SECURITY_SEND_PASSWORD_CHANGED_EMAIL
                            and send_email is None):
              self.send_mail(
                  _('flask_unchained.bundles.security:email_subject.password_changed_notice'),
                  to=user.email,
                  template='security/email/password_changed_notice.html',
                  user=user)
          password_changed.send(app._get_current_object(), user=user)
docs: Service method to change a user's password.
  
          Sends signal `password_changed`.
  
          :param user: The :class:`User`'s password to change.
          :param password: The new password.
          :param send_email: Whether or not to override the config option
                             ``SECURITY_SEND_PASSWORD_CHANGED_EMAIL`` and force
                             either sending or not sending an email.