How to use the tockloader.tbfh.TBFHeader function in tockloader

contained_files = self.tab.getnames()
		# A TBF name is in the format: ..tbf
		for contained_file in contained_files:
			name_pieces = contained_file.split('.')
			if len(name_pieces) >= 2 and name_pieces[-1] == 'tbf':
				if name_pieces[0] == arch:
					matching_tbf_filenames.append(contained_file)

		# Get all of the TBF headers and app binaries to create a TabApp.
		tbfs = []
		for tbf_filename in matching_tbf_filenames:
			binary_tarinfo = self.tab.getmember(tbf_filename)
			binary = self.tab.extractfile(binary_tarinfo).read()

			# First get the TBF header from the correct binary in the TAB
			tbfh = TBFHeader(binary)

			if tbfh.is_valid():
				# Check that total size actually matches the binary that we got.
				if tbfh.get_app_size() < len(binary):
					# It's fine if the binary is smaller, but the binary cannot be
					# longer than the amount of reserved space (`total_size` in the
					# TBF header) for the app.
					raise TockLoaderException('Invalid TAB, the app binary is longer than its defined total_size')

				tbfs.append((tbfh, binary[tbfh.get_size_before_app():]))
			else:
				raise TockLoaderException('Invalid TBF found in app in TAB')

		return TabApp(tbfs)

# erase covers a large area of flash. In that case, we must read all
		# apps and then re-write them, since otherwise they will be erased.
		#
		# So, we iterate through all apps and read them into memory if we are
		# doing an erase and re-flash cycle or if the app has moved.
		app_address = address
		for app in apps:
			# If we do not already have a binary, and any of the conditions are
			# met, we need to read the app binary from the board.
			if (not app.has_app_binary()) and \
			   (self.args.bundle_apps or
			   	app.get_address() != app_address or
			   	app.is_modified()):
					logging.debug('Reading app {} binary from board.'.format(app))
					entire_app = self.channel.read_range(app.address, app.get_size())
					in_flash_tbfh = TBFHeader(entire_app)
					app.set_app_binary(entire_app[in_flash_tbfh.get_header_size():])

			app_address += app.get_size()

		# Need to know the address we are putting each app at.
		app_address = address

		# Actually write apps to the board.
		if self.args.bundle_apps:
			# Tockloader has been configured to bundle all apps as a single
			# binary. Here we concatenate all apps and then call flash once.
			#
			# This should be compatible with all boards, but if there several
			# existing apps they have to be re-flashed, and that could add
			# significant overhead. So, we prefer to flash only what has changed
			# and special case this bundle operation.

# This can be the default, it can be configured in the attributes on
		# the hardware, or it can be passed in to Tockloader.
		address = self.channel.get_apps_start_address()

		# Jump through the linked list of apps
		while (True):
			header_length = 200 # Version 2
			flash = self.channel.read_range(address, header_length)

			# if there was an error, the binary array will be empty
			if len(flash) < header_length:
				break

			# Get all the fields from the header
			tbfh = TBFHeader(flash)

			if tbfh.is_valid():
				app = InstalledApp(tbfh, address)
				apps.append(app)

				address += app.get_size()

			else:
				break

		if self.args.debug:
			logging.debug('Found {} app{} on the board.'.format(len(apps), helpers.plural(len(apps))))
			for i,app in enumerate(apps):
				logging.debug('  {}. {}'.format(i+1, app))

		return apps

def extract_tbf (self, tbf_name):
		'''
		Return a `TabApp` object from this TAB. You must specify the desired TBF
		name, and only that TBF will be returned.
		'''
		tbf_filename = '{}.tbf'.format(tbf_name)
		binary_tarinfo = self.tab.getmember(tbf_filename)
		binary = self.tab.extractfile(binary_tarinfo).read()

		# First get the TBF header from the correct binary in the TAB
		tbfh = TBFHeader(binary)

		if tbfh.is_valid():
			# Check that total size actually matches the binary that we got.
			if tbfh.get_app_size() < len(binary):
				# It's fine if the binary is smaller, but the binary cannot be
				# longer than the amount of reserved space (`total_size` in the
				# TBF header) for the app.
				raise TockLoaderException('Invalid TAB, the app binary is longer than its defined total_size')

			return TabApp([(tbfh, binary[tbfh.get_size_before_app():])])
		else:
			raise TockLoaderException('Invalid TBF found in app in TAB')