Return the self.data index position for the filename.

        Args:
            filename: Name of the file to search for in self.data.

        Returns:
            The self.data index for the filename.  Returns None
            if the filename is not found in self.data.

def has_filename(self, filename):
        """Return the self.data index position for the filename.

        Args:
            filename: Name of the file to search for in self.data.

        Returns:
            The self.data index for the filename.  Returns None
            if the filename is not found in self.data.
        """
        fixpath = lambda path: osp.normcase(osp.realpath(path))
        for index, finfo in enumerate(self.data):
            if fixpath(filename) == fixpath(finfo.filename):
                return index
        return None