code: def remove(group_id, user_id):
      
      group = Group.query.get_or_404(group_id)
      user = User.query.get_or_404(user_id)
  
      if group.can_edit(current_user):
          try:
              group.remove_member(user)
          except Exception as e:
              flash(str(e), "error")
              return redirect(urlparse(request.referrer).path)
  
          flash(_('User %(user_email)s was removed from %(group_name)s group.',
                  user_email=user.email, group_name=group.name), 'success')
          return redirect(urlparse(request.referrer).path)
  
      flash(
          _(
              'You cannot delete users of the group %(group_name)s',
              group_name=group.name
          ),
          'error'
      )
      return redirect(url_for('.index'))
docs: Remove user from a group.