Replace the Excel spreadsheet in the related |EmbeddedXlsxPart| with
        the Excel binary in *xlsx_blob*, adding a new |EmbeddedXlsxPart| if
        there isn't one.

def update_from_xlsx_blob(self, xlsx_blob):
        """
        Replace the Excel spreadsheet in the related |EmbeddedXlsxPart| with
        the Excel binary in *xlsx_blob*, adding a new |EmbeddedXlsxPart| if
        there isn't one.
        """
        xlsx_part = self.xlsx_part
        if xlsx_part is None:
            self.xlsx_part = EmbeddedXlsxPart.new(xlsx_blob, self._package)
            return
        xlsx_part.blob = xlsx_blob