function getLeftmostColKey({ colgroups, colKeys }) {
    return getLeftmostOrRightmostColKey({
        type: "leftmost",
        colgroups,
        colKeys,
    });
}
@getLeftmostColKey
@desc get leftmost column key
@param {array<object>} colgroups
@param {array<any>} colKeys
@return colKey