Searches through a list of filters and finds a specific predicate that should be appended at the top level of a search (i.e., has special requirements for combining with other predicates). Also verifies that the predicate is not combined in any invalid ways.

Combination Requirements:

• Only ONE filter can have a predicate with the target field
• Only ONE predicate with the target field can exist
• The predicate can only be ANDed to other predicates
• The predicate's field value MUST be a string or boolean (not string[] or IMatchOptions)

Example: Portal's bbox field cannot be conditionally searched. Any value provided will always be applied as a top-level filter.

• Valid: ?bbox=1,2,3,4&filter=type:CSV
• Invalid: `?filter=type:CSV OR (type:PDF AND bbox=1,2,3,4)

Parameters

Returns

the predicate (if present and all requirements are met)

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Function defined in common/src/search/_internal/commonHelpers/getTopLevelPredicate.ts:22