Parameters for $actionToLoadSubTables


I am currently using Custom Variables to generate a couple of reports. For one report, Industries, I have an API method called ‘getCompaniesByIndustry’. After reading the documentation, I came up with this line in the Report class:

$this->actionToLoadSubTables = 'getCompaniesByIndustry';

Whenever I try to load the subtable, though, it says “Please specify a value for ‘industry’.” How can I get this API method to use the Industry it is a child of?