src/transformers/models/distilbert/modeling_distilbert.py/FFN/__init__
class FFN:    def __init__(self, config):
        super().__init__()
        self.dropout = nn.Dropout(p=config.dropout)
        self.chunk_size_feed_forward = config.chunk_size_feed_forward
        self.seq_len_dim = 1
        self.lin1 = nn.Linear(in_features=config.dim, out_features=config.hidden_dim)
        self.lin2 = nn.Linear(in_features=config.hidden_dim, out_features=config.dim)
        assert config.activation in ["relu", "gelu"], f"activation ({config.activation}) must be in ['relu', 'gelu']"
        self.activation = gelu if config.activation == "gelu" else nn.ReLU()