code: def _get_module(module_name=None, module=None, register=True):
      
      if module is None and module_name is not None:
          try:
              module = sys.modules[module_name]
          except KeyError as ex:
              print(ex)
              raise KeyError(('module_name=%r must be loaded before ' +
                              'receiving injections') % module_name)
      elif module is not None and module_name is None:
          pass
      else:
          raise ValueError('module_name or module must be exclusively specified')
      if register is True:
          _add_injected_module(module)
      return module
docs: finds module in sys.modules based on module name unless the module has
      already been found and is passed in