## Task
Generate a sorted list of all possible IP addresses in a network.
For a subnet that is not a valid IPv4 network return `None`.
## Examples
```
ipsubnet2list("192.168.1.0/31") == ["192.168.1.0", "192.168.1.1"]
ipsubnet2list("213.256.46.160/28") == None
```
from ipaddress import IPv4Network, AddressValueError

def ipsubnet2list(subnet):
    try: return list(map(str, IPv4Network(subnet).hosts()))
    except AddressValueError: return None
from ipaddress import IPv4Network, AddressValueError

def ipsubnet2list(subnet):
    try: return list(map(str, IPv4Network(subnet).hosts()))
    except AddressValueError: return None