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.

def load(dbname, dbmode='a'):
    """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.
    """
    if dbmode == 'w':
        raise AttributeError("dbmode='w' not allowed for load.")
    db = Database(dbname, dbmode=dbmode)

    return db