code: public java.util.List<ClusterParameterGroup> getParameterGroups() {
          if (parameterGroups == null) {
              parameterGroups = new com.amazonaws.internal.SdkInternalList<ClusterParameterGroup>();
          }
          return parameterGroups;
      }
docs: <p>
  A list of <a>ClusterParameterGroup</a> instances. Each instance describes one cluster parameter group.
  </p>
  
  @return A list of <a>ClusterParameterGroup</a> instances. Each instance describes one cluster parameter group.