import { Sampler } from '@opentelemetry/sdk-trace-base';
/**
 * Parses OTEL_TRACES_SAMPLER_ARG for the `rules` sampler and returns a
 * composite sampler ready for use.
 *
 * Format: semicolon-separated list of key=value rules:
 *   drop=/healthcheck;fallback=parentbased_always_on
 *
 * Supported rules:
 *   drop=<value>    - drop SERVER spans whose url.path/http.target contains <value>
 *   fallback=<name> - fallback sampler; supported: always_on, parentbased_always_on
 *
 * If arg is not set, defaults to no drop rules and parentbased_always_on fallback.
 */
export declare function createRuleBasedSampler(arg: string | undefined): Sampler;
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