input: Write a python function to create and train a simple neural network model using Keras.
  assert create_and_train_model(x_train, y_train) is not None
output: def create_and_train_model(x_train, y_train):
      from tensorflow.keras.models import Sequential
      from tensorflow.keras.layers import Dense
      
      # Create a simple neural network model
      model = Sequential([
          Dense(64, input_shape=(x_train.shape[1],), activation='relu'),
          Dense(64, activation='relu'),
          Dense(1, activation='sigmoid')
      ])
      
      # Compile the model
      model.compile(optimizer='adam', loss='binary_crossentropy', metrics=['accuracy'])
      
      # Train the model
      model.fit(x_train, y_train, epochs=10, batch_size=32, verbose=1)
      
      return model