old_contents: from sqlalchemy import Column, String, Integer
  
  from . import Base
  
  
  class Channel(Base):
      __tablename__ = 'channels'
  
      channel_id = Column(String, primary_key=True, nullable=False)
      vk_group_id = Column(String, nullable=False)
      last_vk_post_id = Column(Integer, nullable=False, server_default='0')
      owner_id = Column(String, nullable=False)
      owner_username = Column(String)
      hashtag_filter = Column(String)
  
new_contents: from sqlalchemy import Column, String, Integer
  
  from . import Base
  
  
  class Channel(Base):
      __tablename__ = 'channels'
  
      channel_id = Column(String, primary_key=True, nullable=False)
      vk_group_id = Column(String, nullable=False)
      last_vk_post_id = Column(Integer, nullable=False, server_default='0', default=0)
      owner_id = Column(String, nullable=False)
      owner_username = Column(String)
      hashtag_filter = Column(String)
  
subject: Fix error 'unorderable types: int() > NoneType()'