Counts all elements contained in the specified element map.
Notes:
GOMElement
type and associated with different keys. However, it will be counted only once.
GOMElement.id).
Two different instances of GOMElement type, e.g.
element1 and element1,
represent the same element when
element1.id == element2.id
elementMapId
Note: When the element map with such an identifier does not exist, the generator raises an error.
getMappedElements(), putMappedElements(), checkElementMap()