code: def parse(cls, fptr, offset, length):
          
          num_bytes = offset + length - fptr.tell()
          read_buffer = fptr.read(num_bytes)
          label = read_buffer.decode('utf-8')
          return cls(label, length=length, offset=offset)
docs: Parse Label box.
  
          Parameters
          ----------
          fptr : file
              Open file object.
          offset : int
              Start position of box in bytes.
          length : int
              Length of the box in bytes.
  
          Returns
          -------
          LabelBox
              Instance of the current label box.