… mechanism.

If there is no mod file for the implementation, returns "".
Note the first line of the code is the name of the modfile.

>>> from neuron import h
>>> s = h.Section(name='s')
>>> mt = h.MechanismType(0)
>>> dir(mt)
['__bool__', '__call__', '__class__', '__delattr__', '__delitem__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__gt__', '__hash__', '__init__', '__iter__', '__le__', '__len__', '__lt__', '__module__', '__ne__', '__new__', '__next__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__setitem__', '__setstate__', '__sizeof__', '__str__', '__subclasshook__', 'action', 'baseattr', 'code', 'count', 'file', 'has_net_event', 'hname', 'hocobjptr', 'internal_type', 'is_artificial', 'is_netcon_target', 'make', 'menu', 'pp_begin', 'pp_next', 'remove', 'same', 'select', 'selected']
>>> mt.select('hh')
0.0
>>> mt.file()
'hh.mod'
>>> print('\n'.join(mt.code().split('\n')[:4]))
TITLE hh.mod   squid sodium, potassium, and leak channels

COMMENT
 This is the original Hodgkin-Huxley treatment for the set of sodium,

a ::: commented full path line if realpath available,
inserts the text of the INCLUDE file,
and closes the text with a ::: commented "end INCLUDE fname" line.