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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 _render_parts(self, header_parts):
 """ Helper function to format and quote a single header. Useful for single headers that are composed of multiple items. E.g., 'Content-Disposition' fields. :param header_parts: A sequence of (k, v) tuples or a :class:`dict` of (k, v) to format """

        parts = []
        iterable = header_parts
        if isinstance(header_parts, dict):
            iterable = header_parts.items()

        for name, value in iterable:
            if value is not None:
                parts.append(self._render_part(name, value))

        return '; '.join(parts)