Question about Zero_module

Hi, thanks for open source the code. It is a great help to understand how to implement Flow matching in practice.

I have a hard time to understand the purpose of `zero_module` function when implement UNET model for Image example. Particularly,
```python
def zero_module(module):
"""
Zero out the parameters of a module and return it.
"""
for p in module.parameters():
p.detach().zero_()
return module
```
In attention block:
```python
self.proj_out = zero_module(conv_nd(1, channels, channels, 1))
```
or ResNet block layer
```
self.out_layers = nn.Sequential(
normalization(self.out_channels),
nn.SiLU(),
nn.Dropout(p=dropout),
zero_module(
conv_nd(dims, self.out_channels, self.out_channels, 3, padding=1)
),
)
```
In these blocks, the final layer in the block are all `zero_module`. Can you point me to the resource to explain why we need to do that? thank you