Why is my code giving errors? What did I do wrong?

# GRADED$\_$CELL

# UNQ$\_$C$1$

num$\_$outputs $=32$

tf$.$random.set$\_$seed$(1)$

user$\_$NN $=$ tf$.$keras.models.Sequential$([$

### START CODE HERE ###

tf$.$keras.layers.Dense$(256,$ activation$=$'relu'$),$

tf$.$keras.layers.Dense$(128,$ activation$=$'relu'$),$

tf$.$keras.layers.Dense$($num$\_$outputs, activation$=$'linear'$),$

### END CODE HERE ###

$])$

item$\_$NN $=$ tf$.$keras.models.Sequential$([$

### START CODE HERE ###

tf$.$keras.layers.Dense$(256,$ activation$=$'relu'$),$

tf$.$keras.layers.Dense$(128,$ activation$=$'relu'$),$

tf$.$keras.layers.Dense$($num$\_$outputs, activation$=$'linear'$),$

### END CODE HERE ###

$])$

# create the user input and point to the base network

input$\_$user $=$ tf$.$keras.layers.Input$($shape$=($num$\_$user$\_$features$))$

vu $=$ user$\_$NN$($input$\_$user$)$

vu $=$ tf$.$linalg.l$2\_$normalize$($vu$,$ axis$=1)$

# create the item input and point to the base network

input$\_$item $=$ tf$.$keras.layers.Input$($shape$=($num$\_$item$\_$features$))$

vm $=$ item$\_$NN$($input$\_$item$)$

vm $=$ tf$.$linalg.l$2\_$normalize$($vm$,$ axis$=1)$

# compute the dot product of the two vectors vu and vm

output $=$ tf$.$keras.layers.Dot$($axes$=1)([$vu$,$ vm$])$

# specify the inputs and output of the model

model $=$ Model$([$input$\_$user, input$\_$item$],$ output$)$

model.summary$()$