Returns (at runtime) the absolute path of the input DDB file.

def ddb_filepath(self):
        """Returns (at runtime) the absolute path of the input DDB file."""
        # This is not very elegant! A possible approach could to be path self.ddb_node.outdir!
        if isinstance(self.ddb_node, FileNode): return self.ddb_node.filepath
        path = self.ddb_node.outdir.has_abiext("DDB")
        return path if path else "DDB_FILE_DOES_NOT_EXIST"