It would be good to document the method signature here; 

Something like this would be ideal for this method; it uses the [yardoc](http://yardoc.org) documentation syntax and explains the expected input and output.

```ruby
# Extract an IP address from the output of the `ifconfig` command
#
# @param output [String] The output of the ifconfig command
# @return [String, nil] A string if an actual IP address was extracted, otherwise nil
def self.parse_inet_address(output)
```