assignlist : assignlist ',' assign \n | assign

def p_assignlist(self,t):
    "assignlist : assignlist ',' assign \n | assign"
    if len(t)==4: t[0] = t[1] + [t[3]]
    elif len(t)==2: t[0] = [t[1]]
    else: raise NotImplementedError('unk_len', len(t)) # pragma: no cover