func (s SourceSelectionCriteria) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
	if err := e.EncodeToken(start); err != nil {
		return err
	}
	if s.IsValid() {
		if err := e.EncodeElement(s.ReplicaModifications, xml.StartElement{Name: xml.Name{Local: "ReplicaModifications"}}); err != nil {
			return err
		}
	}
	return e.EncodeToken(xml.EndElement{Name: start.Name})

	if err := e.EncodeToken(start); err != nil {
		return err
	}
	if err := e.EncodeElement(d.String(), xml.StartElement{Name: xml.Name{Local: "Bucket"}}); err != nil {
		return err
	}
	if d.StorageClass != "" {
		if err := e.EncodeElement(d.StorageClass, xml.StartElement{Name: xml.Name{Local: "StorageClass"}}); err != nil {
			return err
		}
	}
	return e.EncodeToken(xml.EndElement{Name: start.Name})
}

// MarshalXML - produces the xml representation of the Filter struct
// only one of Prefix, And and Tag should be present in the output.
func (f Filter) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
	if err := e.EncodeToken(start); err != nil {
		return err
	}

	switch {
	case !f.And.isEmpty():
		if err := e.EncodeElement(f.And, xml.StartElement{Name: xml.Name{Local: "And"}}); err != nil {
			return err
		}

	}

	if len(s.Items) == 0 {
		return nil
	}

	if err := e.EncodeToken(start); err != nil {
		return err
	}

	for _, item := range s.Items {
		if err := e.Encode(xmlKeyEntry{
			XMLName: xxml.Name{Local: item.Key},
			Value:   item.Value,
		}); err != nil {
			return err
		}
	}

	return e.EncodeToken(start.End())
}

pkg encoding, type TextUnmarshaler interface, UnmarshalText([]uint8) error
pkg encoding/xml, method (*Encoder) EncodeElement(interface{}, StartElement) error
pkg encoding/xml, method (*Encoder) EncodeToken(Token) error
pkg encoding/xml, method (*Encoder) Flush() error
pkg encoding/xml, method (StartElement) End() EndElement
pkg encoding/xml, type Marshaler interface { MarshalXML }