In the coding exercise attatched below, I dont understand why we load the parameters Wya and by but we never calculate their gradients.

def rnn_cell_backward(da_next, cache):

“”"

Implements the backward pass for the RNN-cell (single time-step).

```
Arguments:
da_next -- Gradient of loss with respect to next hidden state
cache -- python dictionary containing useful values (output of rnn_cell_forward())
Returns:
gradients -- python dictionary containing:
dx -- Gradients of input data, of shape (n_x, m)
da_prev -- Gradients of previous hidden state, of shape (n_a, m)
dWax -- Gradients of input-to-hidden weights, of shape (n_a, n_x)
dWaa -- Gradients of hidden-to-hidden weights, of shape (n_a, n_a)
dba -- Gradients of bias vector, of shape (n_a, 1)
"""
# Retrieve values from cache
(a_next, a_prev, xt, parameters) = cache
# Retrieve values from parameters
Wax = parameters["Wax"]
Waa = parameters["Waa"]
Wya = parameters["Wya"]
ba = parameters["ba"]
by = parameters["by"]
### START CODE HERE ###
# compute the gradient of dtanh term using a_next and da_next (≈1 line)
dtanh = None
# compute the gradient of the loss with respect to Wax (≈2 lines)
dxt = None
dWax = None
# compute the gradient with respect to Waa (≈2 lines)
da_prev = None
dWaa = None
# compute the gradient with respect to b (≈1 line)
dba = None
### END CODE HERE ###
# Store the gradients in a python dictionary
gradients = {"dxt": dxt, "da_prev": da_prev, "dWax": dWax, "dWaa": dWaa, "dba": dba}
return gradients
```