code: def RegisterTextKey(cls, key, atomid):
          
          def getter(tags, key):
              return tags[atomid]
  
          def setter(tags, key, value):
              tags[atomid] = value
  
          def deleter(tags, key):
              del(tags[atomid])
  
          cls.RegisterKey(key, getter, setter, deleter)
docs: Register a text key.
  
          If the key you need to register is a simple one-to-one mapping
          of MP4 atom name to EasyMP4Tags key, then you can use this
          function::
  
              EasyMP4Tags.RegisterTextKey("artist", "\xa9ART")