code: def load(dbname, dbmode='a'):
      
      if dbmode == 'w':
          raise AttributeError("dbmode='w' not allowed for load.")
      db = Database(dbname, dbmode=dbmode)
  
      return db
docs: Load an existing hdf5 database.
  
      Return a Database instance.
  
      :Parameters:
        filename : string
          Name of the hdf5 database to open.
        mode : 'a', 'r'
          File mode : 'a': append, 'r': read-only.