code: def transform_sources(self, sources, with_string=False):
          
          modules = {}
          updater = partial(
              self.replace_source, modules=modules, prefix='string_')
          for filename in sources:
              updated = update_func_body(sources[filename], updater)
              sources[filename] = EXTERN_AND_SEG + updated
          logging.debug('modules: %s', modules)
          return sources, self.build_funcs(modules)
docs: Get the defintions of needed strings and functions
          after replacement.