text: from sqlalchemy.ext.declarative import declarative_base
  from sqlalchemy import (Column, BigInteger, Integer, String, DateTime, Boolean, Text)
  from sqlalchemy.sql.schema import ForeignKey
  
  Base = declarative_base()
  
  class User(Base):
      __tablename__ = 'user'
      
      id = Column(BigInteger, primary_key=True, autoincrement=True)
      username = Column(String(32), unique=True, nullable=False)
      avatar_url = Column(Text, nullable=False)
      email = Column(String(32), unique=True, nullable=False)
      hashed_password = Column(String(80), nullable=False)
      created_time = Column(DateTime, nullable=False)
      last_login = Column(DateTime, nullable=True)
      is_super = Column(Boolean, default=False, nullable=False)
      banned = Column(Boolean, default=False, nullable=False)
      
  
  class Secret(Base):
      __tablename__ = 'secret'
      
      id = Column(BigInteger, primary_key=True, autoincrement=True)
      creator = Column(BigInteger, ForeignKey('user.id'), nullable=False)
      content = Column(Text, nullable=False)
      created_time = Column(DateTime, nullable=False)
      modified_time = Column(DateTime)
      like_count = Column(Integer, default=0, nullable=False)
      hug_count = Column(Integer, default=0, nullable=False)
      banned = Column(Boolean, default=False, nullable=False)
      
      
  class Comment(Base):
      __tablename__ = 'comment'
      
      id = Column(BigInteger, primary_key=True, autoincrement=True)
      belong_to = Column(BigInteger, ForeignKey('secret.id'), nullable=False)
      creator = Column(BigInteger, ForeignKey('user.id'), nullable=False)
      content = Column(Text, nullable=False)
      created_time = Column(DateTime, nullable=False)
      modified_time = Column(DateTime)
      like_count = Column(Integer, default=0, nullable=False)
      banned = Column(Boolean, default=False, nullable=False)
  