<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _missing_imageinfo(self):
 """ returns list of image filenames that are missing info """

        if 'image' not in self.data:
            return
        missing = []
        for img in self.data['image']:
            if 'url' not in img:
                missing.append(img['file'])
        return list(set(missing))