Move group to another position in group's parent.
        
        index must be a valid index of group.parent.groups

def move_group_in_parent(self, group = None, index = None):
        """Move group to another position in group's parent.
        
        index must be a valid index of group.parent.groups

        """
        
        if group is None or index is None:
            raise KPError("group and index must be set")
        elif type(group) is not v1Group or type(index) is not int:
            raise KPError("group must be a v1Group-instance and index "
                          "must be an integer.")
        elif group not in self.groups:
            raise KPError("Given group doesn't exist")
        elif index < 0 or index >= len(group.parent.children):
            raise KPError("index must be a valid index if group.parent.groups")
        else:
            group_at_index = group.parent.children[index]
            pos_in_parent = group.parent.children.index(group) 
            pos_in_groups = self.groups.index(group)
            pos_in_groups2 = self.groups.index(group_at_index)

            group.parent.children[index] = group
            group.parent.children[pos_in_parent] = group_at_index
            self.groups[pos_in_groups2] = group
            self.groups[pos_in_groups] = group_at_index
            if group.children:
                self._move_group_helper(group)
            if group_at_index.children:
                self._move_group_helper(group_at_index)
            group.last_mod = datetime.now().replace(microsecond=0)
            return True