code: @SuppressWarnings("unchecked")
  	public T setHeaders(final Map<String, List<String>> headers) {
  		this.headers = headers;
  		return (T) this;
  	}
docs: Sets all of the headers in one call.
  
  @param headers
  A Map of headers, where the header name is a String, and the value is a List of one or more values.
  @return this Message, to support chained method calls