code: def register():
      """Register a new user.
  
      Validates that the username is not already taken. Hashes the
      password for security.
      """
      if request.method == "POST":
          username = request.form["username"]
          password = request.form["password"]
          error = None
  
          if not username:
              error = "Username is required."
          elif not password:
              error = "Password is required."
          elif db.session.execute(
              db.select(
                  db.select(User).filter_by(username=username).exists()
              )
          ).scalar():
              error = f"User {username} is already registered."
  
          if error is None:
              # the name is available, create the user and go to the login page
              db.session.add(User(username=username, password=password))
              db.session.commit()
              return redirect(url_for("auth.login"))
  
          flash(error)
  
      return render_template("auth/register.html")
  
file_path: flask-sqlalchemy/examples/flaskr/flaskr/auth/views.py
imports: import functools
  from flask import Blueprint
  from flask import flash
  from flask import g
  from flask import redirect
  from flask import render_template
  from flask import request
  from flask import session
  from flask import url_for
  from flaskr import db
  from flaskr.auth.models import User
label_desc: Use image node_id 3 for calling a global function with example usage: register() and returns: render_template, redirect