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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 inject_environment_variables(self, d):
 """ Recursively injects environment variables into TOML values """


        if not d:
            return d
        if isinstance(d, six.string_types):
            return os.path.expandvars(d)
        for k, v in d.items():
            if isinstance(v, six.string_types):
                d[k] = os.path.expandvars(v)
            elif isinstance(v, dict):
                d[k] = self.inject_environment_variables(v)
            elif isinstance(v, list):
                d[k] = [self.inject_environment_variables(e) for e in v]

        return d