| BreadthConceptHierarchyIterator | 
 Iterates hierarchy of concepts, breadth-first. 
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| DepthFirstConceptIterator | 
Traverse hierarchy of  SConcepts for a given concept (inclusive), visiting super-concepts first
 then super-interfaces in an order they were specified in super-concepts (breadth-like).  
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| DescendantsTreeIterator | 
Iterator for a  SNode sub-tree.  
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| FilterIterator<T> | 
Iterator that uses  Condition to filter out undesired elements.  
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| ImmediateParentConceptIterator | 
 Concept hierarchy iterator that walks direct super concepts only, up to specified concept (exclusive)
 or a top-most concept (BaseConcept, inclusive). 
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| InstanceOfCondition | 
 SNode condition which is satisfied with an instance of specified concept. 
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| TreeFilterIterator<T> | 
 Iterator that uses condition to filter out complete sub-tree. 
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| UniqueIterator<T> | 
 Ensures elements coming from iterator are unique. 
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