Flask login with wtfoms validation

gistfile1.txt

class LoginForm(flask_wtf.Form):
    """
    Validate login from
    """
    email_validator = [flask_wtf.Required()]
    pwd_validator = [flask_wtf.Required(), flask_wtf.Length(2)]

    email = flask_wtf.TextField(u'email', validators=email_validator)
    password = flask_wtf.PasswordField(u'password', validators=pwd_validator)
    submit = flask_wtf.SubmitField("Login")

    def _get_user(self, email):
        return mongo.db.users.find_one({'email': email})

    def validate_email(self, field):
        if not self._get_user(field.data):
            raise flask_wtf.ValidationError("Invalid email")

    def validate_password(self, field):
        user = self._get_user(self.email.data)
        if user and user[u'password'] != field.data:
            raise flask_wtf.ValidationError("Invalid password")


class Login(MethodView):

    def __init__(self):
        self.form = LoginForm()

    def get(self):
        return flask.render_template('login.html', login_form=self.form)

    def post(self):
        if self.form.validate():
            flask.session['user'] = self.form.email.data
            flask.flash('You were logged in')
            return flask.redirect(flask.url_for("index"))
        return flask.render_template('login.html', login_form=self.form)


app.add_url_rule('/login',
                 view_func=Login.as_view('login'),
                 methods=['POST', 'GET'])

Is this valid? The docs say it should be, for example, validate_email(form, field) not validate_email(self,field)