Use puppet to append to a file on one node

We have an existing puppet setup that is working well. However, on one node, I want to append a line to a configuration file. How do I do that?

The file is currently fully defined in a manifest. The .pp file includes a file { ... } paragraph with a 'content' attribute that is good for all the other hosts. I have a node/name.yaml file for the node on which I want to append one more line to the file. How do I specify that in the .yaml file? Alternatively, how may I override the entire file {...} paragraph in the .yaml file?