public RequestSpecBuilder addHeader(String headerName, String headerValue) {
        spec.header(headerName, headerValue);
        return this;
    }
public RequestSpecBuilder addHeader ( String headerName , String headerValue ) { spec . header ( headerName , headerValue ) ; return this ; }
Add a header to be sent with the request e.g:

@param headerName  The header name
@param headerValue The header value
@return The request specification builder