code: private String getBaseString() {
  		if (!hasTs()) {
  			throw new IllegalStateException(
  					"This HawkWwwAuthenticateContext has no timestamp");
  		}
  		return new StringBuilder(HAWK_TS_PREFIX).append(SLF).append(getTs())
  				.append(SLF).toString();
  	}
docs: Generate base string for timestamp HMAC generation.
  
  @return