src/transformers/models/distilbert/modeling_distilbert.py/TransformerBlock/__init__
class TransformerBlock:    def __init__(self, config):
        super().__init__()

        assert config.dim % config.n_heads == 0

        self.attention = MultiHeadSelfAttention(config)
        self.sa_layer_norm = nn.LayerNorm(normalized_shape=config.dim, eps=1e-12)

        self.ffn = FFN(config)
        self.output_layer_norm = nn.LayerNorm(normalized_shape=config.dim, eps=1e-12)