text: from flask_login import current_user
  from flask_wtf import FlaskForm
  from flask_wtf.file import FileField, FileAllowed
  from wtforms import StringField, PasswordField, SubmitField, BooleanField
  from wtforms.validators import DataRequired, Length, Email, EqualTo, ValidationError
  
  from app.models import User
  
  
  class RegistrationForm(FlaskForm):
      username = StringField('Username',
                             validators=[DataRequired(), Length(min=2, max=20)])
      email = StringField('Email',
                          validators=[DataRequired(), Email()])
      password = PasswordField('Password', validators=[DataRequired()])
      confirm_password = PasswordField('Confirm Password',
                                       validators=[DataRequired(), EqualTo('password')])
      submit = SubmitField('Sign Up')
  
      def validate_username(self, username):
          user = User.query.filter_by(username=username.data).first()
          if user:
              raise ValidationError('Username already exists, choose another')
  
      def validate_email(self, email):
          user = User.query.filter_by(email=email.data).first()
          if user:
              raise ValidationError('That email already exists, choose another')
  
  class LoginForm(FlaskForm):
      email = StringField('Email',
                          validators=[DataRequired(), Email()])
      password = PasswordField('Password', validators=[DataRequired()])
      remember = BooleanField('Remember Me')
      submit = SubmitField('Login')
  
  class UpdateAccountForm(FlaskForm):
      username = StringField('Username',
                             validators=[DataRequired(), Length(min=2, max=20)])
      email = StringField('Email',
                          validators=[DataRequired(), Email()])
      picture = FileField('Update profile picture', validators=[FileAllowed(['jpg', 'png'])])
      submit = SubmitField('Update')
  
      def validate_username(self, username):
          if username.data != current_user.username:
              user = User.query.filter_by(username=username.data).first()
              if user:
                  raise ValidationError('That username is taken. Please choose a different one.')
  
      def validate_email(self, email):
          if email.data != current_user.email:
              user = User.query.filter_by(email=email.data).first()
              if user:
                  raise ValidationError('That email is taken. Please choose a different one.')
  