old_contents: from flask_wtf import Form
  from wtforms import StringField, DateTimeField,PasswordField, IntegerField
  from wtforms validators import DataRequired
  
  class login(Form):
      username=StringField("username",validators=[DataRequired()])
      password = PasswordField('password', validators=[DataRequired()])
  
  class post_data(Form):
      id=IntegerField("id",validators=[DataRequired()])
      post=StringField("post",validators=[DataRequired()])
      date_time=DateTimeField("date_time",validators=[DataRequired()])
      title=StringField("title",validators=[DataRequired()])
      tag=StringField("tag",validators=[DataRequired()])
  
new_contents: from flask_wtf import Form
  from wtforms import StringField, DateTimeField,PasswordField, IntegerField
  from wtforms.validators import DataRequired
  
  class login(Form):
      username=StringField("username",validators=[DataRequired()])
      password = PasswordField('password', validators=[DataRequired()])
  
  class post_data(Form):
      id=IntegerField("id",validators=[DataRequired()])
      post=StringField("post",validators=[DataRequired()])
      date_time=DateTimeField("date_time",validators=[DataRequired()])
      title=StringField("title",validators=[DataRequired()])
      tag=StringField("tag",validators=[DataRequired()])
  
subject: Update forms.py