def list_available_request_headers(custom_headers:nil)
      response = list_available_request_headers_async(custom_headers:custom_headers).value!
      response.body unless response.nil?
    end
def list_available_request_headers(custom_headers:nil)
      response = list_available_request_headers_async(custom_headers:custom_headers).value!
      response.body unless response.nil?
    end
Lists all available request headers.

 @param custom_headers [Hash{String => String}] A hash of custom headers that
 will be added to the HTTP request.

 @return [Array] operation results.