loss = smp.utils.losses.DiceLoss()，metrics = [ smp.utils.metrics.IoU(threshold=0.5), ] optimizer = torch.optim.Adam([ dict(params=model1.parameters(), lr=0.0001), ])请输出unet分割训练及验证代码

以下是unet分割训练及验证代码：

# 导入必要的库
import torch
import torch.nn as nn
import torch.optim as optim
from torch.utils.data import DataLoader
import segmentation_models_pytorch as smp

# 定义模型
model = smp.Unet(
encoder_name="resnet18", # 使用resnet18作为编码器
encoder_weights="imagenet", # 使用预训练的imagenet权重
in_channels=3, # 输入通道数为3
classes=1 # 输出通道数为1
)

# 定义损失函数、优化器和评价指标
loss = smp.utils.losses.DiceLoss()
metrics = [
smp.utils.metrics.IoU(threshold=0.5),
]
optimizer = torch.optim.Adam([
dict(params=model.parameters(), lr=0.0001),
])

# 定义训练和验证函数
def train(model, dataloader, loss_fn, optimizer):
model.train()
train_loss = 0.0
train_iou = 0.0
for inputs, targets in dataloader:
inputs = inputs.cuda()
targets = targets.cuda()
optimizer.zero_grad()
outputs = model(inputs)
loss = loss_fn(outputs, targets)
loss.backward()
optimizer.step()
train_loss += loss.item()
train_iou += metrics[0](outputs, targets).item()
train_loss /= len(dataloader)
train_iou /= len(dataloader)
return train_loss, train_iou

def validate(model, dataloader, loss_fn, metrics):
model.eval()
val_loss = 0.0
val_iou = 0.0
with torch.no_grad():
for inputs, targets in dataloader:
inputs = inputs.cuda()
targets = targets.cuda()
outputs = model(inputs)
loss = loss_fn(outputs, targets)
val_loss += loss.item()
val_iou += metrics[0](outputs, targets).item()
val_loss /= len(dataloader)
val_iou /= len(dataloader)
return val_loss, val_iou

# 加载数据集
train_dataset = MyDataset(train_data)
val_dataset = MyDataset(val_data)
train_dataloader = DataLoader(train_dataset, batch_size=16, shuffle=True)
val_dataloader = DataLoader(val_dataset, batch_size=16, shuffle=False)

# 开始训练
for epoch in range(10):
train_loss, train_iou = train(model, train_dataloader, loss, optimizer)
val_loss, val_iou = validate(model, val_dataloader, loss, metrics)
print("Epoch: {}, Train Loss: {:.4f}, Train IoU: {:.4f}, Val Loss: {:.4f}, Val IoU: {:.4f}".format(epoch+1, train_loss, train_iou, val_loss, val_iou))