old_contents: import os
  
  
  class Config(object):
      """Parent configuration class."""
      DEBUG = False
      CSRF_ENABLED = True
      SECRET = os.getenv('SECRET')
      SQLALCHEMY_DATABASE_URI = os.getenv('DATABASE_URL')
  
  
  class DevelopmentConfig(Config):
      """Configurations for Development."""
      DEBUG = True
  
  
  class TestingConfig(Config):
      """Configurations for Testing, with a separate test database."""
      TESTING = True
      SQLALCHEMY_DATABASE_URI = 'postgresql://localhost/test_db'
      DEBUG = True
  
  
  class StagingConfig(Config):
      """Configurations for Staging."""
      DEBUG = True
  
  
  class ProductionConfig(Config):
      """Configurations for Production."""
      DEBUG = False
      TESTING = False
  
  
  app_config = {
      'development': DevelopmentConfig,
      'testing': TestingConfig,
      'staging': StagingConfig,
      'production': ProductionConfig,
  }
  
new_contents: import os
  
  
  class Config(object):
      """Parent configuration class."""
      DEBUG = False
      CSRF_ENABLED = True
      SECRET = os.getenv('SECRET')
      SQLALCHEMY_DATABASE_URI = os.getenv('DATABASE_URL')
  
  
  class DevelopmentConfig(Config):
      """Configurations for Development."""
      DEBUG = True
      SQLALCHEMY_DATABASE_URI = 'postgresql://localhost/flask_api'
  
  
  class TestingConfig(Config):
      """Configurations for Testing, with a separate test database."""
      TESTING = True
      SQLALCHEMY_DATABASE_URI = 'postgresql://localhost/test_db'
      DEBUG = True
  
  
  class StagingConfig(Config):
      """Configurations for Staging."""
      DEBUG = True
  
  
  class ProductionConfig(Config):
      """Configurations for Production."""
      DEBUG = False
      TESTING = False
  
  
  app_config = {
      'development': DevelopmentConfig,
      'testing': TestingConfig,
      'staging': StagingConfig,
      'production': ProductionConfig,
  }
  
subject: Set up development database