code: public String[] listProviders() {
  		String[] providers = new String[container.size()];
  
  		int i = 0;
  		Iterator<String> ki = container.keySet().iterator();
  		while(ki.hasNext()) {
  			providers[i++] = (String) ki.next();	
  		}
  		
  		return providers;
  	}
docs: List the MetricsProvider keys in this MetricsContainer.
  @return a String[] containing the MetricsProvider keys.