import { ChatResponse } from '../chat';
import { Usage } from '../chat/metadata';
/**
 * An utility class to provide support methods handling {@link Usage}.
 */
export declare abstract class UsageUtil {
    /**
     * Accumulate usage tokens from the previous chat response to the current usage
     * tokens.
     * @param currentUsage the current usage.
     * @param previousChatResponse the previous chat response.
     * @return accumulated usage.
     */
    static getCumulativeUsage(currentUsage: Usage, previousChatResponse?: ChatResponse): Usage;
    static isEmpty(usage: Usage | null): boolean;
}
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