The getAvailableOptions(String fieldName) method on any Issue object, such as the one provided by the issue, linkedIssue and parentIssue variables (where applicable), as well as Issue objects returned by other methods such as getParentObject(), getEpic() or getLinkedIssues(), returns a collection of available options for the specified field. The return type depends on the field specified. For example, a version picker type field returns a Collection<Version>, the Component/s field returns a Collection<ProjectComponent>, etc.
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