@staticmethod<EOL><INDENT>def _compound_column_value(k1, k2):<DEDENT>
k1 = ProjectStats._column_value(k1)<EOL>k2 = ProjectStats._column_value(k2)<EOL>if k1 == '<STR_LIT>' and k2 == '<STR_LIT>':<EOL><INDENT>return '<STR_LIT>'<EOL><DEDENT>return '<STR_LIT>' % (k1, k2)<EOL>
Like :py:meth:`~._column_value` but collapses two unknowns into one.

:param k1: first (top-level) value
:param k2: second (bottom-level) value
:return: display key
:rtype: str