Deleting content objects is done by IObjectManager.
Example:
# manage_delObjects takes list of ids as an argument
folder.manage_delObjects(["list", "of", "ids", "to", "delete"])
Or:
parent = context.aq_parent
parent.manage_delObjects([context.getId()])
Little tricky. An example:
ids = folder.objectIds() # Plone 3 or older
ids = folder.keys() # Plone 4 or newer
if len(ids) > 0:
# manage_delObject will mutate the list
# so we cannot give it tuple returned by objectIds()
ids = list(ids)
folder.manage_delObjects(ids)