def METHOD_NAME(level, files='all'):
    """
    Set the global Sage verbosity level.
    INPUT:
    - ``level`` -- an integer between 0 and 2, inclusive.
    - ``files`` (default: 'all'): list of files to make verbose, or
       'all' to make ALL files verbose (the default).
    OUTPUT: changes the state of the verbosity flag and possibly
    appends to the list of files that are verbose.
    EXAMPLES::
        sage: set_verbose(2)
        sage: verbose("This is Sage.", level=1)  # not tested
        VERBOSE1 (?): This is Sage.
        sage: verbose("This is Sage.", level=2)  # not tested
        VERBOSE2 (?): This is Sage.
        sage: verbose("This is Sage.", level=3)  # not tested
        [no output]
        sage: set_verbose(0)
    """
    if level is None:
        level = -1
    if isinstance(level, str):
        set_verbose_files([level])
    global LEVEL
    LEVEL = level
    if isinstance(files, str):
        files = [files]
    set_verbose_files(files)