stmt_list : stmt
              | stmt_list stmt

def p_stmt_list(p):
    """
    stmt_list : stmt
              | stmt_list stmt
    """
    if len(p) == 2:
        p[0] = node.stmt_list([p[1]] if p[1] else [])
    elif len(p) == 3:
        p[0] = p[1]
        if p[2]:
            p[0].append(p[2])
    else:
        assert 0