src/transformers/models/xlm/modeling_xlm.py/TransformerFFN/__init__
class TransformerFFN:    def __init__(self, in_dim, dim_hidden, out_dim, config):
        super().__init__()
        self.dropout = config.dropout
        self.lin1 = nn.Linear(in_dim, dim_hidden)
        self.lin2 = nn.Linear(dim_hidden, out_dim)
        self.act = gelu if config.gelu_activation else nn.functional.relu
        self.chunk_size_feed_forward = config.chunk_size_feed_forward
        self.seq_len_dim = 1