ipython/ipython — pull request #3907 by jdfreder (2013-08-05 17:38:23+00:00)
Title: nbconvert: Remove cell from worksheet if null.

If someone wants to write a simple by-cell transformer that drops certain cells, the should be able to do something like the following:

def transform_cell(self, cell, resources, index):
if condition:
return None, resources
else:
return cell, resources

This does not work in the current master. Instead, the None gets set in the dict, then the template finds a None cell and either errors or inserts an `Unknown cell type` into the results.