NsContentNameAsIdList : NsContentNameAsId
                          | NsContentNameAsIdList COMMA NsContentNameAsId

def p_NsContentNameAsIdList(p):
    '''
    NsContentNameAsIdList : NsContentNameAsId
                          | NsContentNameAsIdList COMMA NsContentNameAsId
    '''
    if len(p) == 2:
        p[0] = NsContentNameAsIdList(None, p[1])
    else:
        p[0] = NsContentNameAsIdList(p[1], p[3])