function extractContentType$6(body) {
	if (body === null) {
		// body is null
		return null;
	} else if (typeof body === 'string') {
		// body is string
		return 'text/plain;charset=UTF-8';
	} else if (isURLSearchParams$5(body)) {
		// body is a URLSearchParams
		return 'application/x-www-form-urlencoded;charset=UTF-8';
	} else if (isBlob$6(body)) {
		// body is blob
		return body.type || null;
	} else if (Buffer.isBuffer(body)) {
		// body is buffer
		return null;
	} else if (Object.prototype.toString.call(body) === '[object ArrayBuffer]') {
		// body is ArrayBuffer
		return null;
	} else if (ArrayBuffer.isView(body)) {
		// body is ArrayBufferView
		return null;
	} else if (typeof body.getBoundary === 'function') {
		// detect form data input from form-data module
		return `multipart/form-data;boundary=${body.getBoundary()}`;
	} else if (body instanceof Stream$2) {
		// body is stream
		// can't really do much about this
		return null;
	} else {
		// Body constructor defaults other things to string
		return 'text/plain;charset=UTF-8';
	}
}
Performs the operation "extract a `Content-Type` value from |object|" as
specified in the specification:
https://fetch.spec.whatwg.org/#concept-bodyinit-extract

This function assumes that instance.body is present.

@param   Mixed  instance  Any options.body input