Lớp encoder transformer

class EncoderLayer(nn.Module):
    def __init__(self, d_model, num_heads, d_ff, dropout):
        super().__init__()
        # Instantiate the layers
        self.self_attn = ____(d_model, num_heads)
        self.ff_sublayer = ____(d_model, d_ff)
        self.norm1 = ____
        self.norm2 = ____
        self.dropout = nn.Dropout(dropout)

    def forward(self, x, src_mask):
        # Complete the forward method
        attn_output = self.____
        x = self.norm1(x + self.dropout(attn_output))
        ff_output = self.____
        x = self.norm2(x + self.dropout(ff_output))
        return x