<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def exists(self, filename):
 """Report whether a file exists on all distribution points. Determines file type by extension. Args: filename: Filename you wish to check. (No path! e.g.: "AdobeFlashPlayer-14.0.0.176.pkg") Returns: Boolean """

        result = True
        for repo in self._children:
            if not repo.exists(filename):
                result = False
        return result