import type { SamplingContext } from './internal/types.cjs';
/**
 * Every operation is reported at least once, but every next occurrence is decided by the sampler.
 */
export declare function atLeastOnceSampler(config: {
    /**
     * Produces a unique key for a given GraphQL request.
     * This key is used to determine the uniqueness of a GraphQL operation.
     */
    keyFn(context: SamplingContext): string;
    sampler(context: SamplingContext): number | boolean;
}): (context: SamplingContext) => boolean;
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