old_contents: from flask_wtf import Form
  from wtforms import TextAreaField, StringField, SelectField, BooleanField
  from wtforms.validators import InputRequired, Optional, Length
  
  class PostForm(Form):
      title = StringField('제목', validators=[InputRequired(), Length(max=120)])
      body = TextAreaField('내용', validators=[InputRequired()])
      private = BooleanField('이 글을 비공개로 작성합니다', default=True)
      tags = StringField('글갈피', validators=[Length(max=100)])
      category = SelectField('분류', validators=[Optional()],
              choices=[('everyday', 'EVERYDAY'),
                  ('study', 'STUDY'),
                  ('idea', 'IDEA'),
                  ('world', 'WORLD')])
  
new_contents: from flask_wtf import Form
  from wtforms import TextAreaField, StringField, SelectField, BooleanField
  from wtforms.validators import InputRequired, Optional, Length
  
  class PostForm(Form):
      title = StringField('제목', validators=[InputRequired(), Length(max=120)])
      body = TextAreaField('내용', validators=[InputRequired()])
      private = BooleanField('비공개 설정', default=True)
      tags = StringField('글갈피', validators=[Length(max=100)])
      category = SelectField('분류', validators=[Optional()],
              choices=[('everyday', 'EVERYDAY'),
                  ('study', 'STUDY'),
                  ('idea', 'IDEA'),
                  ('world', 'WORLD')])
  
subject: Change label text of 'private' Field