I just started to learn python2.7, compared to the examples in the book, but when I write here, I always report grammatical errors. 
 looked at it, and searched the Internet, but didn"t find out where the mistake was. 
this is the source code:
class User(db.Model):
    __tablename__ = "users"
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(64), unique=True, index=True)
    role_id = db.Column(db.Integer, db.ForeignKey("roles.id")
    def __repr__(self):
        return "<User %r>" % self.username
this is the compilation error:
  File "hello.py", line 44
    def __repr__(self):
      ^
SyntaxError: invalid syntax
