Expects a dictionary with the keys being instances of ``KVField.key_type``
            and the values being instances of ``KVField.value_type``.  After validation,
            the dictionary is transformed into a list of dictionaries with ``k`` and ``v``
            fields set to the keys and values from the original dictionary.

def wrap(self, value):
        ''' Expects a dictionary with the keys being instances of ``KVField.key_type``
            and the values being instances of ``KVField.value_type``.  After validation,
            the dictionary is transformed into a list of dictionaries with ``k`` and ``v``
            fields set to the keys and values from the original dictionary.
        '''
        self.validate_wrap(value)
        ret = []
        for k, v in value.items():
            k = self.key_type.wrap(k)
            v = self.value_type.wrap(v)
            ret.append( { 'k' : k, 'v' : v })
        return ret