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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 get_course_completions(cls, user, course_key):
 """ Returns a dictionary mapping BlockKeys to completion values for all BlockCompletion records for the given user and course_key. Return value: dict[BlockKey] = float """

        user_course_completions = cls.user_course_completion_queryset(user, course_key)
        return cls.completion_by_block_key(user_course_completions)