Loss function for multi-label classification

Binary Cross Entropy is used for multi-label classification, and it's involved with a sigmoid function. (Note that cross-entropy is used for multi-class classification that's involved with a softmax function) (reference)

• Example of a simple neural network model for multi-label classification in Keras (link)
  - Size of an output layer must be a number of labels.
• [PyTorch web] BCEWithLogitLoss (link)