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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 by_name(cls, name):
 """Returns the unique object representing the goal of the specified name. :API: public """

    if name not in cls._goal_by_name:
      cls._goal_by_name[name] = _Goal(name)
    return cls._goal_by_name[name]