term : STR
                | NONE
                | dtype

def p_term(self, p):
        '''term : STR
                | NONE
                | dtype'''
        if p[1] == 'str':
            p[0] = str
        elif p[1] == 'None':
            p[0] = type(None)
        else:
            p[0] = p[1][0]