code: def init(uri, echo=False):
      
      global ENGINE, _METADATA, JOBS_TABLE, METADATA_TABLE, LOGS_TABLE
      ENGINE = sqlalchemy.create_engine(uri, echo=echo, convert_unicode=True)
      _METADATA = sqlalchemy.MetaData(ENGINE)
      JOBS_TABLE = _init_jobs_table()
      METADATA_TABLE = _init_metadata_table()
      LOGS_TABLE = _init_logs_table()
      _METADATA.create_all(ENGINE)
docs: Initialise the database.
  
      Initialise the sqlalchemy engine, metadata and table objects that we use to
      connect to the database.
  
      Create the database and the database tables themselves if they don't
      already exist.
  
      :param uri: the sqlalchemy database URI
      :type uri: string
  
      :param echo: whether or not to have the sqlalchemy engine log all
          statements to stdout
      :type echo: bool