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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 variables(self):
 """Returns the list of all tf.Variables created by module instantiation."""

    result = []
    for _, value in sorted(self.variable_map.items()):
      if isinstance(value, list):
        result.extend(value)
      else:
        result.append(value)
    return result