create_sequences

# create sequences of images, input sequences and output words for an image
def create_sequences(tokenizer, max_length, descriptions, photos, vocab_size):
	X1, X2, y = list(), list(), list()
	# walk through each image identifier
	for key, desc_list in descriptions.items():
		# walk through each description for the image
		for desc in desc_list:
			# encode the sequence
			seq = tokenizer.texts_to_sequences([desc])[0]
			# split one sequence into multiple X,y pairs
			for i in range(1, len(seq)):
				# split into input and output pair
				in_seq, out_seq = seq[:i], seq[i]
				# pad input sequence
				in_seq = pad_sequences([in_seq], maxlen=max_length)[0]
				# encode output sequence
				out_seq = to_categorical([out_seq], num_classes=vocab_size)[0]
				# store
				X1.append(photos[key][0])
				X2.append(in_seq)
				y.append(out_seq)
	return array(X1), array(X2), array(y)