old_contents: import os
  
  from sqlalchemy.ext.automap import automap_base
  from sqlalchemy.orm import sessionmaker
  from sqlalchemy import create_engine
  from sqlalchemy.orm.scoping import scoped_session
  
  DB_URL = os.environ.get('DB_URL')
  
  if not DB_URL:
      raise ValueError("DB_URL not present in the environment")
  
  Base = automap_base()
  engine = create_engine(DB_URL, pool_size=8, max_overflow=2)
  Base.prepare(engine, reflect=True)
  
  session_factory  = sessionmaker(bind=engine, expire_on_commit=False)
  Session = scoped_session(session_factory)
new_contents: import os
  
  from sqlalchemy.ext.automap import automap_base
  from sqlalchemy.orm import sessionmaker
  from sqlalchemy import create_engine
  from sqlalchemy.orm.scoping import scoped_session
  from sqlalchemy.pool import NullPool
  
  DB_URL = os.environ.get('DB_URL')
  
  if not DB_URL:
      raise ValueError("DB_URL not present in the environment")
  
  Base = automap_base()
  engine = create_engine(DB_URL, poolclass=NullPool)
  Base.prepare(engine, reflect=True)
  
  session_factory  = sessionmaker(bind=engine, expire_on_commit=False)
  Session = scoped_session(session_factory)
subject: Disable connection pooling.