Allow specifying code location

[ranigb]

It would be great if a snippet could be targeted at specific locations in the code. For example, if the code to add imports could be directly sent to the first cell even if I am somewhere else in the code. Furthermore, if parts of the snippet can go in different places that would be even better. This will allow adding profiling to a notebook in which case you may wish to run something at the beginning of the notebook (say, start a data collection process) and run the analysis at the end of the notebook.