Message Text
Extensions must define @apply, @ns and @at
Cause
Implementation of a custom constraint requires implementation of a parsing function. A custom constraint has been specified, but the configuration is incorrect or does not refer to a parsing function.
Response
Check your search options node with search:check-options to ensure it is valid. Validate that the custom library module is available at the expected path, and that the namespace and local name correctly refer to a function in that module.
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