bug: `TNS` truthiness is wrong.

[python-processing-unit]

According the specification section 4:

Conditions accept INT, STR, or TNS. STR conditions are first converted to INT using the INT built-in rules (empty -> 0; binary string -> that integer; other non-empty -> 1) before truthiness is checked. A TNS condition is true if any of its elements is true by the INT/STR truthiness rules.

In the implementation, however, TNS is always falsey.