关于torch.nn.Linear的权重shape一点疑问

import torch
a = torch.randn(60, 30)  # 
b = torch.nn.Linear(30, 15)  # 但是b的weight的shape是[15,30]
output = b(a) #猜测是Linear会对权重做转置
print('b.weight.shape:\n ', b.weight.shape)
print('b.bias.shape:\n', b.bias.shape)
print('output.shape:\n', output.shape)


ans = torch.mm(a, b.weight.t()) + b.bias #这里也是将b转置才可以计算，结果和上面是一致的. 
print('ans.shape:\n', ans.shape)

print(torch.equal(ans, output))