How to use the mido.set_backend function in mido

def connect(self):
        print('Connecting MIDI devices')
        mido.set_backend('mido.backends.rtmidi')
        controllerNames = mido.get_input_names()

        if not controllerNames: return

        for name in controllerNames:
            try:
                cleanName = name[:name.rfind(' ')]
                print("Connecting " + cleanName)
                mido.open_input(name, callback=lambda m, cn=cleanName: self.onMessage(cn, m))
            except Exception as e:
                print('Unable to open MIDI input: {}'.format(name), file=sys.stderr)

# Setup GPIO buttons
for button in config.buttons['stomp_buttons']:
    GPIO.setup(button, GPIO.IN, pull_up_down=GPIO.PUD_UP) 
    GPIO.add_event_detect(button, GPIO.RISING, bouncetime=500, callback=buttonPressed)
# Setup events for bank up and down buttons
GPIO.setup(config.buttons['bank_button_up'], GPIO.IN, pull_up_down=GPIO.PUD_UP)
GPIO.setup(config.buttons['bank_button_down'], GPIO.IN, pull_up_down=GPIO.PUD_UP)
GPIO.add_event_detect(config.buttons['bank_button_up'], GPIO.BOTH, bouncetime=500, callback=bank_change)
GPIO.add_event_detect(config.buttons['bank_button_down'], GPIO.BOTH, bouncetime=500, callback=bank_change)

# Display loading screen, will probably only display if clear_true is true
print_lcd("Loading...","")

# Backend stuff
mido.set_backend(config.katana['backend'])

# Load parameter metadata
rangeObj = Range(config.files['ranges_file'])

# Load presets
banks = PresetsHandler.load_presets(config.files['preset_file'])

# Setup amp
katana = Katana(config.katana['amp'], config.katana['channel'], config.katana['clear_input'])
print_lcd("Katana Ready", "Select Patch")
            
try:
    while (True):
        c = str(input("> "))
        if c == "list":
            for i in banks:

"""
Try out the new printer port backend.

It also works with MIDO_BACKEND, so you can do:

    $ MIDO_BACKEND=printer python
    >>> import mido
    >>> mido.get_output_names()
    ['The Printer Port']
"""
import mido

mido.set_backend('printer')

print('Available outputs: {!r}'.format(mido.get_output_names()))

with mido.open_output() as port:
    print('Using {}.'.format(port))

    port.send(mido.Message('program_change', program=10))
    for i in [1, 2, 3]:
        port.send(mido.Message('control_change', control=1, value=i))

result.append( {"group":"simple", "category":category, "type":type} )

        # Complex devices have distinct parameter address ranges, so do all
        # colors
        for category in self.complex:
            for color in self.name2enum.keys():
                idx = self.assign_index2[category][color]
                type = katana.query_sysex_byte( assign_base_addr, idx )
                result.append( {"group":"complex", "category":category, "type":type} )

        return result

if __name__ == '__main__':
    from katana import Katana
    import mido
    mido.set_backend('mido.backends.rtmidi')

    args = sys.argv
    buttonObj = ColorButtons( args[1] )

    katana = Katana( "KATANA:KATANA MIDI 1 20:0", 1, False )
    result = buttonObj.read_knobs( katana )
    pprint( result )

    result = buttonObj.read_color_assign( katana )
    pprint( result )

_DEFAULT_METRONOME_PROGRAM = 117  # Melodic Tom
_DEFAULT_METRONOME_MESSAGES = [
    mido.Message(type='note_on', note=44, velocity=64),
    mido.Message(type='note_on', note=35, velocity=64),
    mido.Message(type='note_on', note=35, velocity=64),
    mido.Message(type='note_on', note=35, velocity=64),
]
_DEFAULT_METRONOME_CHANNEL = 1

# 0-indexed.
_DRUM_CHANNEL = 9

try:
  # The RtMidi backend is easier to install and has support for virtual ports.
  import rtmidi  # pylint: disable=unused-import,g-import-not-at-top
  mido.set_backend('mido.backends.rtmidi')
except ImportError:
  # Tries to use PortMidi backend by default.
  tf.logging.warn('Could not import RtMidi. Virtual ports are disabled.')


class MidiHubError(Exception):  # pylint:disable=g-bad-exception-name
  """Base class for exceptions in this module."""
  pass


def get_available_input_ports():
  """Returns a list of available input MIDI ports."""
  return mido.get_input_names()


def get_available_output_ports():

def do_start_logging(self, midi_port_name):
		logging.info("start midi logging on {}".format(midi_port_name))

		self.do_stop_logging()
		MidiLogMessageHandler.midi_port_name = midi_port_name

		try:
			mido.set_backend('mido.backends.rtmidi/UNIX_JACK')
			MidiLogMessageHandler.mido_port = mido.open_input(self.midi_port_name, callback=self.on_midi_in)
		except:
			logging.error("Can't open MIDI Port {}".format(self.midi_port_name))

blocks = [ [global_base, global_parms['length']], [dsp_base, dsp_parms['length']] ]

        # Both mod and fx share the same global key setting
        if name == "PitchShifter":
            extra = [ self.master_key['baseAddr'], self.master_key['length'] ]
            blocks.append( extra )
        
        return { "name":name, "blocks":blocks }
        
            
if __name__ == '__main__':
    from katana import Katana
    import mido
    from color_buttons import ColorButtons

    mido.set_backend('mido.backends.rtmidi')

    args = sys.argv
    buttonObj = ColorButtons( args[1] )

    katana = Katana( "KATANA:KATANA MIDI 1 20:0", 1, False )
    dsp_recs = buttonObj.read_knobs( katana )

    # pprint( dsp_recs )

    complexObj = ComplexDSP( args[2] )
    
    for dsp_rec in dsp_recs:
        if dsp_rec['group'] == 'complex':
            coords = complexObj.get_coords( dsp_rec['category'], dsp_rec['type'] ) 
            print( "Name: ", coords['name'], ", Blocks: ", coords['blocks'] )

# coding: utf-8
import mido
from wcwidth import wcswidth
from pgpal.compat import pg, textwrap, unicode_literals
from pgpal.configpage import pyform
from pgpal.const import *
from pgpal import configspec, config, vdt

mido.set_backend('mido.backends.pygame')

translations = {
    'path': '目录',
    'volume': '音量',
    'chip': '芯片',
    'full': '全',
    'screen': '屏',
    'use': '使用',
    'font': '字体',
    'file': '文件',
    'samplerate': '采样率',
    'window': '窗口',
    'music': '音乐',
    'game': '游戏',
    'enable': '启用',
    'port': '端口',