import { ConceptAs } from '@dolittle/concepts';
/**
 * Represents a projection key.
 */
export declare class Key extends ConceptAs<string, '@dolittle/sdk.projections.Key'> {
    /**
     * Initializes a new instance of {@link Key}.
     * @param {string} key - The expression that specifices the key selection.
     */
    constructor(key: string);
    /**
     * Creates a {@link Key} from a string.
     * @param {Key | any} key - The projection key.
     * @returns {Key} The projection key concept.
     */
    static from(key: Key | any): Key;
}
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