`KEYIN` allows any type for `key`.

[python-processing-unit]

According to the specification section 9.1.7:

• BOOL: KEYIN(INT|FLT|STR: key, MAP: map) and BOOL: VALUEIN(ANY: value, MAP: map) = MUST return TRUE when the given key or value occurs in map and FALSE otherwise.

In the implementation, however, KEYIN allows any type for key.