Replace concat function with min, max, sum or Hadamard function in implementation of graph attention network using dgl

Question

I'm using dgl implementation of graph attention network code in python:

    Understand Graph Attention Network — DGL 0.6.1

And I want to use min, max, sum or Hadamard function instead of concatenation function in equation (2) of the implementation. How can I do this?

The code of equation (2) is below:

class GATLayer(nn.Module):
    def __init__(self, g, in_dim, out_dim):
        super(GATLayer, self).__init__()
        self.g = g
        # equation (1)
        self.fc = nn.Linear(in_dim, out_dim, bias=False)
        # equation (2)
        self.attn_fc = nn.Linear(2 * out_dim, 1, bias=False)
        self.reset_parameters()

    def reset_parameters(self):
        gain = nn.init.calculate_gain('relu')
        nn.init.xavier_normal_(self.fc.weight, gain=gain)
        nn.init.xavier_normal_(self.attn_fc.weight, gain=gain)

    def edge_attention(self, edges):
        # edge UDF for equation (2)
        z2 = torch.cat([edges.src['z'], edges.dst['z']], dim=1)
        a = self.attn_fc(z2)
        return {'e': F.leaky_relu(a)}

    def message_func(self, edges):
        # message UDF for equation (3) & (4)
        return {'z': edges.src['z'], 'e': edges.data['e']}

And the concatenation function is torch.cat() in the below code:

class MultiHeadGATLayer(nn.Module):
    def __init__(self, g, in_dim, out_dim, num_heads, merge='cat'):
        super(MultiHeadGATLayer, self).__init__()
        self.heads = nn.ModuleList()
        for i in range(num_heads):
            self.heads.append(GATLayer(g, in_dim, out_dim))
        self.merge = merge

    def forward(self, h):
        head_outs = [attn_head(h) for attn_head in self.heads]
        if self.merge == 'cat':
            # concat on the output feature dimension (dim=1)
            #return torch.min(torch.stack(head_outs), dim=1)
            return torch.cat(head_outs, dim=1)
        else:
            # merge using average
            return torch.mean(torch.stack(head_outs))

How can I change the concatenation function of the original implementation?