docs: def simple_transpile_modname_source_target(
              self, spec, modname, source, target):
          """
          The original simple transpile method called by compile_transpile
          on each target.
          """
  
          opener = self.opener
          bd_target = self._generate_transpile_target(spec, target)
          logger.info('Transpiling %s to %s', source, bd_target)
          with opener(source, 'r') as reader, opener(bd_target, 'w') as _writer:
              writer = SourceWriter(_writer)
              self.transpiler(spec, reader, writer)
              if writer.mappings and spec.get(GENERATE_SOURCE_MAP):
                  source_map_path = bd_target + '.map'
                  with open(source_map_path, 'w') as sm_fd:
                      self.dump(encode_sourcemap(
                          filename=bd_target,
                          mappings=writer.mappings,
                          sources=[source],
                      ), sm_fd)
  
                  # just use basename
                  source_map_url = basename(source_map_path)
                  _writer.write('\n//# sourceMappingURL=')
                  _writer.write(source_map_url)
                  _writer.write('\n')