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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 get_distinfo_file(self, path):
 """ Returns a path located under the ``.dist-info`` directory. Returns a string representing the path. :parameter path: a ``'/'``-separated path relative to the ``.dist-info`` directory or an absolute path; If *path* is an absolute path and doesn't start with the ``.dist-info`` directory path, a :class:`DistlibException` is raised :type path: str :rtype: str """

        # Check if it is an absolute path  # XXX use relpath, add tests
        if path.find(os.sep) >= 0:
            # it's an absolute path?
            distinfo_dirname, path = path.split(os.sep)[-2:]
            if distinfo_dirname != self.path.split(os.sep)[-1]:
                raise DistlibException(
                    'dist-info file %r does not belong to the %r %s '
                    'distribution' % (path, self.name, self.version))

        # The file must be relative
        if path not in DIST_FILES:
            raise DistlibException('invalid path for a dist-info file: '
                                   '%r at %r' % (path, self.path))

        return os.path.join(self.path, path)