def _set_hash(self):
        if not self.data_file:
            return None

        file_exists = self.data_file.storage.exists(self.data_file.name)

        if (file_exists and self.data_file.name != '') \
                or (not file_exists and self.data_file):
            try:
                self.data_file.seek(os.SEEK_SET)
            except __HOLE__:
                return u''
            else:
                self.file_hash = u'md5:%s' \
                    % md5(self.data_file.read()).hexdigest()

                return self.file_hash

        return u''
dataset/ETHPy150Open kobotoolbox/kobocat/onadata/apps/main/models/meta_data.py/MetaData._set_hash