code: def get_connection(module_name: str, connection: Optional[str] = None) -> str:
      
      # 1. Use given connection
      if connection is not None:
          return connection
  
      module_name = module_name.lower()
      module_config_cls = get_module_config_cls(module_name)
      module_config = module_config_cls.load()
  
      return module_config.connection or config.connection
docs: Return the SQLAlchemy connection string if it is set.
  
      Order of operations:
  
      1. Return the connection if given as a parameter
      2. Check the environment for BIO2BEL_{module_name}_CONNECTION
      3. Look in the bio2bel config file for module-specific connection. Create if doesn't exist. Check the
         module-specific section for ``connection``
      4. Look in the bio2bel module folder for a config file. Don't create if doesn't exist. Check the default section
         for ``connection``
      5. Check the environment for BIO2BEL_CONNECTION
      6. Check the bio2bel config file for default
      7. Fall back to standard default cache connection
  
      :param module_name: The name of the module to get the configuration for
      :param connection: get the SQLAlchemy connection string
      :return: The SQLAlchemy connection string based on the configuration