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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def contents(self, path, ref=None):
 """Get the contents of the file pointed to by ``path``. If the path provided is actually a directory, you will receive a dictionary back of the form:: { 'filename.md': Contents(), # Where Contents an instance 'github.py': Contents(), } :param str path: (required), path to file, e.g. github3/repo.py :param str ref: (optional), the string name of a commit/branch/tag. Default: master :returns: :class:`Contents <github3.repos.contents.Contents>` or dict if successful, else None """

        url = self._build_url('contents', path, base_url=self._api)
        json = self._json(self._get(url, params={'ref': ref}), 200)
        if isinstance(json, dict):
            return Contents(json, self)
        elif isinstance(json, list):
            return dict((j.get('name'), Contents(j, self)) for j in json)
        return None