public MetricsConnection header(String headerName, String headerValue) {
        this.headers.put(headerName, headerValue);
        return this;
    }
public MetricsConnection header ( String headerName , String headerValue ) { this . headers . put ( headerName , headerValue ) ; return this ; }
Sets value for specific header

@param headerName - header to be set
@param headerValue - value of the header
@return