import torch
from torch import nn

class AdaptiveConcatPool2d(nn.Module):
    def __init__(self, sz=None):
        super().__init__()
        sz = sz or (1,1)
        self.ap = nn.AdaptiveAvgPool2d(sz)
        self.mp = nn.AdaptiveMaxPool2d(sz)
    def forward(self, x): return torch.cat([self.mp(x), self.ap(x)], 1)

class Lambda(nn.Module):
    def __init__(self, f): super().__init__(); self.f=f
    def forward(self, x): return self.f(x)

class Flatten(nn.Module):
    def __init__(self): super().__init__()
    def forward(self, x): return x.view(x.size(0), -1)