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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 Parse(self, stat, knowledge_base):
 """Expand any variables in the value."""

    value = stat.registry_data.GetValue()
    if not value:
      raise parser.ParseError("Invalid value for key %s" % stat.pathspec.path)
    value = artifact_utils.ExpandWindowsEnvironmentVariables(
        value, knowledge_base)
    if value:
      yield rdfvalue.RDFString(value)