/**
 * Normalizes header keys, e.g. "content-type" to "Content-Type"
 * @param record any headers object you wish to normalize
 * @param replacementCharacter e.g. '_' to change "Content-Type" to "Content_Type"
 * @param filter_regexp undesirable characters, e.g. /[^a-z]+/g
 * @returns a new object (inputs are not mutated)
 */
export declare function sanitizeHeaders(
	record: Record<string, any>,
	replacementCharacter?: string,
	filter_regexp?: RegExp
): Record<string, string>;
export default sanitizeHeaders;