为什么这段代码不管用？我尝试了所有方法，但都没有有效

Question

import tensorflow as tf
from keras.preprocessing.sequence import Tokenizer
from keras.utils import pad_sequences

# Set parameters
vocab_size = 5000
embedding_dim = 64
max_length = 100
trunc_type='post'
padding_type='post'
oov_tok = "<OOV>"
training_size = len(processed_data)

 # Create tokenizer
tokenizer = Tokenizer(num_words=vocab_size, oov_token=oov_tok)
tokenizer.fit_on_sequences(processed_data)
word_index = tokenizer.word_index

# Create sequences
sequences = tokenizer.texts_to_sequences(processed_data)
padded_sequences = pad_sequences(sequences, maxlen=max_length, padding=padding_type, truncating=trunc_type)

# Create training data
training_data = padded_sequences[:training_size]
training_labels = padded_sequences[:training_size]

# Build model
model = tf.keras.Sequential([
    tf.keras.layers.Embedding(vocab_size, embedding_dim, input_length=max_length),
    tf.keras.layers.Dropout(0.2),
    tf.keras.layers.Conv1D(64, 5, activation='relu'),
    tf.keras.layers.MaxPooling1D(pool_size=4),
    tf.keras.layers.LSTM(64),
    tf.keras.layers.Dense(64, activation='relu'),
    tf.keras.layers.Dense(vocab_size, activation='softmax')
])

# Compile model
model.compile(loss='sparse_categorical_crossentropy', optimizer='adam', metrics=['accuracy'])

# Train model
num_epochs = 50
history = model.fit(training_data, training_labels, epochs=num_epochs, verbose=2)

def predict_answer(model, tokenizer, question):
    # Preprocess question
    question = preprocess(question)
    # Convert question to sequence
    sequence = tokenizer.texts_to_sequences([question])
    # Pad sequence
    padded_sequence = pad_sequences(sequence, maxlen=max_length, padding=padding_type, truncating=trunc_type)
    # Predict answer
    pred = model.predict(padded_sequence)[0]
    # Get index of highest probability
    idx = np.argmax(pred)
    # Get answer
    answer = tokenizer.index_word[idx]
    return answer

# Start chatbot
while True:
    question = input('You: ')
    answer = predict_answer(model, tokenizer, question)
    print('Chatbot:', answer)

在终端里有一个可以发送聊天信息的地方。当我输入我的消息时，它却出现了一个错误：

Traceback (most recent call last):
   File "<stdin>", line 3, in <module>
   NameError: name 'model' is not defined