code: def find_module(self, mod_fullname, path=None):
          
  
          parent_frame = inspect.currentframe().f_back
          while in_importlib(parent_frame):
              parent_frame = parent_frame.f_back
  
          # this line is saying "hey, does mod_fullname exist as a name we've
          # defind previously?"  the purpose of this is to ensure that
          # mod_fullname is really a thing we've defined.  if we haven't defined
          # it before, then we "can't" import from it
          module = fetch_module_from_frame(mod_fullname, parent_frame)
          if not module:
              return None
  
          # make sure it's a class we're allowed to import from
          if module.__class__.__name__ not in self.restrict_to:
              return None
  
          return self
docs: mod_fullname doubles as the name of the VARIABLE holding our new sh
          context.  for example:
  
              derp = sh()
              from derp import ls
  
          here, mod_fullname will be "derp".  keep that in mind as we go throug
          the rest of this function