Returns all elements contained in the specified element map.
Notes:
GOMElement
type and associated with different keys. However, it will be included only once
in the result enumeration.
GOMElement.id).
Two different instances of GOMElement type, e.g.
element1 and element1,
represent the same element when
element1.id == element2.id
elementMapId
countMappedElements(), getElementMapKeys(), putMappedElements()