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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 file_ref(self):
 """Return a string for the file, row and column of the term."""

        from metatab.util import slugify

        assert self.file_name is None or isinstance(self.file_name, str)

        if self.file_name is not None and self.row is not None:
            parts = split(self.file_name);
            return "{} {}:{} ".format(parts[-1], self.row, self.col)
        elif self.row is not None:
            return " {}:{} ".format(self.row, self.col)
        else:
            return ''