export declare function accumulatorSum(groupDocs: Record<string, unknown>[], expr: unknown): number;
export declare function accumulatorAvg(groupDocs: Record<string, unknown>[], expr: unknown): number | null;
export declare function accumulatorMin(groupDocs: Record<string, unknown>[], expr: unknown): unknown;
export declare function accumulatorMax(groupDocs: Record<string, unknown>[], expr: unknown): unknown;
export declare function accumulatorFirst(groupDocs: Record<string, unknown>[], expr: unknown): unknown;
export declare function accumulatorLast(groupDocs: Record<string, unknown>[], expr: unknown): unknown;
export declare function accumulatorPush(groupDocs: Record<string, unknown>[], expr: unknown): unknown[];
export declare function accumulatorAddToSet(groupDocs: Record<string, unknown>[], expr: unknown): unknown[];
export declare function accumulatorStdDevPop(groupDocs: Record<string, unknown>[], expr: unknown): number | null;
export declare function accumulatorStdDevSamp(groupDocs: Record<string, unknown>[], expr: unknown): number | null;
export declare function accumulatorCount(groupDocs: Record<string, unknown>[]): number;
export declare const BUILT_IN_ACCUMULATORS: Record<string, (groupDocs: Record<string, unknown>[], expr: unknown) => unknown>;