def parse(self, value):
        """
        Convert a dictionary of {relative index: value} to a list of parsed
        C{value}s.
        """
        indices = []
        if not isinstance(value, dict):
            # We interpret non-list inputs as a list of one element, for
            # compatibility with certain EC2 APIs.
            return [self.item.coerce(value)]
        for index in value.keys():
            try:
                indices.append(int(index))
            except ValueError:
                raise UnknownParameterError(index)
        result = [None] * len(value)
        for index_index, index in enumerate(sorted(indices)):
            v = value[str(index)]
            if index < 0:
                raise UnknownParameterError(index)
            result[index_index] = self.item.coerce(v)
        return result
Convert a dictionary of {relative index: value} to a list of parsed
        C{value}s.