# processors
On this page we’ll be using this private helper to process a notebook
and return the results, to simplify testing:
``` python
def _run_procs(procs=None, return_nb=False, path=_test_file):
nbp = NBProcessor(path, procs)
nbp.process()
if return_nb: return nbp.nb
return '\n'.join([str(cell) for cell in nbp.nb.cells])
```
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source
### populate_language
``` python
def populate_language(
nb
):
```
*Set cell language based on NB metadata and magics*
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source
### insert_warning
``` python
def insert_warning(
nb
):
```
*Insert Autogenerated Warning Into Notebook after the first cell.*
This preprocessor inserts a warning in the markdown destination that the
file is autogenerated. This warning is inserted in the second cell so we
do not interfere with front matter.
``` python
res = _run_procs(insert_warning)
assert "