code: public DnsServersOptionsModifyStructure withCustomDnsServers(String... customDnsServers) {
          if (this.customDnsServers == null) {
              setCustomDnsServers(new com.amazonaws.internal.SdkInternalList<String>(customDnsServers.length));
          }
          for (String ele : customDnsServers) {
              this.customDnsServers.add(ele);
          }
          return this;
      }
docs: <p>
  The IPv4 address range, in CIDR notation, of the DNS servers to be used. You can specify up to two DNS servers.
  Ensure that the DNS servers can be reached by the clients. The specified values overwrite the existing values.
  </p>
  <p>
  <b>NOTE:</b> This method appends the values to the existing list (if any). Use
  {@link #setCustomDnsServers(java.util.Collection)} or {@link #withCustomDnsServers(java.util.Collection)} if you
  want to override the existing values.
  </p>
  
  @param customDnsServers
  The IPv4 address range, in CIDR notation, of the DNS servers to be used. You can specify up to two DNS
  servers. Ensure that the DNS servers can be reached by the clients. The specified values overwrite the
  existing values.
  @return Returns a reference to this object so that method calls can be chained together.