/**
 * Triangular Moving Average (TRIMA).
 * A triangular-weighted moving average implemented via two `sma` passes.
 * Preserves NaN handling by delegating to `sma` implementations.
 * @param source Input series
 * @param period Window length (must be > 0)
 * @returns Float64Array of TRIMA values (NaN where undefined)
 */
export declare function trima(source: ArrayLike<number>, period: number): Float64Array;