def _ParseYamlFile(self, basepath, basename, parser):
    file_name = self._FindYaml(basepath, basename)
    if file_name is not None:
      fh = self.opener(file_name, 'r')
      try:
        defns = parser(fh, open_fn=self.opener)
      finally:
        fh.close()
      return defns
    return None
Take a RenderedLayer and turn it into a Mapnik input file clause
dataset/ETHPy150Open AppScale/appscale/AppServer/google/appengine/tools/appcfg.py/AppCfgApp._ParseYamlFile--crossover with--dataset/ETHPy150Open hydroshare/hydroshare2/ga_resources/drivers/__init__.py/compile_layer