ValueError: setting an array element with a sequence when training a VGG16 model on a regression problem to generate bounding box coordinates

Question

I am trying to use a custom Huber loss function for my regression problem and train a VGG16 model to generate bounding box coordinates. The code is given below:

def huber(true, pred, delta=1.0):
    loss = np.where(np.abs(true-pred) < delta , 0.5*((true-pred)**2), delta*np.abs(true - pred) - 0.5*(delta**2))
    return np.sum(loss)

...
...
...
model.compile(optimizer=Adam(lr=0.001), loss=huber)

Upon running the script, I get an error with the use of the custom Huber loss function:

model.compile(optimizer=Adam(lr=0.001), loss=huber)

  File "C:\Users\...\lib\site-packages\keras\engine\training.py", line 342, in compile
    sample_weight, mask)

  File "C:\Users\...\lib\site-packages\keras\engine\training_utils.py", line 404, in weighted
    score_array = fn(y_true, y_pred)

  File "C:\Users\...\train_code.py", line 157, in huber
    loss = np.where(np.abs(true-pred) < delta , 0.5*((true-pred)**2), delta*np.abs(true - pred) - 0.5*(delta**2))

  File "<__array_function__ internals>", line 6, in where

ValueError: setting an array element with a sequence.