code: def new(cls, xlsx_blob, package):
          
          partname = package.next_partname(cls.partname_template)
          content_type = CT.SML_SHEET
          xlsx_part = cls(partname, content_type, xlsx_blob, package)
          return xlsx_part
docs: Return a new |EmbeddedXlsxPart| instance added to *package* and
          containing *xlsx_blob*.