code: public CacheSubnetGroup withSubnets(Subnet... subnets) {
          if (this.subnets == null) {
              setSubnets(new com.amazonaws.internal.SdkInternalList<Subnet>(subnets.length));
          }
          for (Subnet ele : subnets) {
              this.subnets.add(ele);
          }
          return this;
      }
docs: <p>
  A list of subnets associated with the cache subnet group.
  </p>
  <p>
  <b>NOTE:</b> This method appends the values to the existing list (if any). Use
  {@link #setSubnets(java.util.Collection)} or {@link #withSubnets(java.util.Collection)} if you want to override
  the existing values.
  </p>
  
  @param subnets
  A list of subnets associated with the cache subnet group.
  @return Returns a reference to this object so that method calls can be chained together.