'Return content types XML mapping each part in *parts* to the
appropriate content type and suitable for storage as
``[Content_Types].xml`` in an OPC package.'

@classmethod
def from_parts(cls, parts):

    cti = cls()
    cti._defaults['rels'] = CT.OPC_RELATIONSHIPS
    cti._defaults['xml'] = CT.XML
    for part in parts:
        cti._add_content_type(part.partname, part.content_type)
    return cti
