The TransformerEncoder block does the following:

Applies self-attention to encode context from the input sequence
Processes the attended input through a feedforward neural network
Stacks multiple of these layers to capture long-range dependencies

So in short, it encodes a sequence using stacked self-attention and feedforward layers.
spam fails_task lang_mismatch pii not_appropriate hate_speech sexual_content quality toxicity humor helpfulness creativity violence