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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_current(cls):
 """Get the context for the current env, if there is one. Returns: `ResolvedContext`: Current context, or None if not in a resolved env. """

        filepath = os.getenv("REZ_RXT_FILE")
        if not filepath or not os.path.exists(filepath):
            return None

        return cls.load(filepath)