def modify_item(self, item, offset, len):
    ' Modify offset and length of ITEM. '
    values = self.by_item[item]
    values[0] = ('%x' % offset)
    values[1] = ('%x' % len)
    self._write()
Modify offset and length of ITEM.
def modify_item(self, item, offset, len):
    '  '
    values = self.by_item[item]
    values[0] = ('%x' % offset)
    values[1] = ('%x' % len)
    self._write()