rule_expression_from_gtv
Takes a GTV representation of one rule, and converts it into a single rule_expression
Throws "INVALID RULE" if the first component of the gtv can't be mapped into a rule_operator value or the second one can't be mapped into a rule_variable value.
Throws if gtv is not the GTV representation of a rule, for example:
it is not a
listthe first two components are not
textsthe last component is not an integer
Parameters
gtv
the rule that should be deserialized