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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 resolve_meta_key(hub, key, meta):
 """ Resolve a value when it's a string and starts with '>' """

    if key not in meta:
        return None
    value = meta[key]
    if isinstance(value, str) and value[0] == '>':
        topic = value[1:]
        if topic not in hub:
            raise KeyError('topic %s not found in hub' % topic)
        return hub[topic].get()
    return value