func (c *Client) ListGroups() (*Groups, error) {
	url := umGroups() + `?depth=` + c.client.depth + `&pretty=` + strconv.FormatBool(c.client.pretty)
	ret := &Groups{}
	err := c.client.Get(url, ret, http.StatusOK)
	return ret, err
}
func (c *Client) ListGroups() (*Groups, error) {
	url := umGroups() + `?depth=` + c.client.depth + `&pretty=` + strconv.FormatBool(c.client.pretty)
	ret := &Groups{}
	err := c.client.Get(url, ret, http.StatusOK)
	return ret, err
}
//ListGroups lists all groups