Callable : NsContentName LPARENT
             | NsContentName SCOPEOP INDENTIFIER LPARENT
             | Expression LPARENT
             | STATIC SCOPEOP INDENTIFIER LPARENT

def p_Callable(p):
    '''
    Callable : NsContentName LPARENT
             | NsContentName SCOPEOP INDENTIFIER LPARENT
             | Expression LPARENT
             | STATIC SCOPEOP INDENTIFIER LPARENT
    '''
    if len(p) <= 3:
        p[0] = Callable(p[1], None)
    else:
        p[0] = Callable(p[1], p[3])