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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 ensure_frequencies(self, frequencies):
 """Ensure frequencies is dict of host-frequencies."""

        if not frequencies:
            return {}
        if not isinstance(frequencies, dict):
            raise ValueError("frequencies should be dict")
        frequencies = {
            host: Frequency.ensure_frequency(frequencies[host]) for host in frequencies
        }
        return frequencies