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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 pickle_dict(items):
    '''Returns a new dictionary where values which aren't instances of
    basestring are pickled. Also, a new key '_pickled' contains a comma
    separated list of keys corresponding to the pickled values.
    '''
    ret = {}
    pickled_keys = []
    for key, val in items.items():
        if isinstance(val, basestring):
            ret[key] = val
        else:
            pickled_keys.append(key)
            ret[key] = pickle.dumps(val)
    if pickled_keys:
        ret['_pickled'] = ','.join(pickled_keys)
    return ret