TabError: inconsistent use of tabs and spaces in indication

When trying to create a simple login form using Flask and Flask-wtf,

confirm_password=Password('Password', validators=[DataRequired(), EqualTo(')])
                                                                                   ^
TabError: inconsistent use of tabs and spaces in indication

An error similar to

I understand that the error is caused by tabs and indentation, but no matter how many times I fix it, it looks like this. - will occur.

How can we solve this problem?Please give me an answer.
Below is the code where the error occurred.

from flash_wtf import FlashForm
from wtforms import StringField, PasswordField, SubmitField, BooleanField
from wtforms.validators import DataRequired, Length, Email

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=Password('Password', validators=[DataRequired(), EqualTo(')])

    submit=SubmitField('Sign Up')

class LoginForm (FlaskForm):
    email=StringField('Email', validators=[DataRequired(), Email()])

    password=PasswordField('password', validators=[DataRequired()])

    remember=BooleanField('Remember Me')

    submit=SubmitField('Login')