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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _find_experiment_tag(self):
 """Finds the experiment associcated with the metadata.EXPERIMENT_TAG tag. Caches the experiment if it was found. Returns: The experiment or None if no such experiment is found. """

    with self._experiment_from_tag_lock:
      if self._experiment_from_tag is None:
        mapping = self.multiplexer.PluginRunToTagToContent(
            metadata.PLUGIN_NAME)
        for tag_to_content in mapping.values():
          if metadata.EXPERIMENT_TAG in tag_to_content:
            self._experiment_from_tag = metadata.parse_experiment_plugin_data(
                tag_to_content[metadata.EXPERIMENT_TAG])
            break
    return self._experiment_from_tag