the binary tree abstract data type as an abstract data typea binary tree is specialization of tree that supports three additional accessor methodst left( )return the position that represents the left child of por none if has no left child right( )return the position that represents the right child of por none if has no right child sibling( )return the position that represents the sibling of por none if has no sibling just as in section for the tree adtwe do not define specialized update methods for binary trees here insteadwe will consider some possible update methods when we describe specific implementations and applications of binary trees the binarytree abstract base class in python just as tree was defined as an abstract base class in section we define new binarytree class associated with the binary tree adt we rely on inheritance to define the binarytree class based upon the existing tree class howeverour binarytree class remains abstractas we still do not provide complete specifications for how such structure will be represented internallynor implementations for some necessary behaviors our python implementation of the binarytree class is given in code fragment by using inheritancea binary tree supports all the functionality that was defined for general trees ( parentis leafrootour new class also inherits the nested position class that was originally defined within the tree class definition in additionthe new class provides declarations for new abstract methods left and right that should be supported by concrete subclasses of binarytree our new class also provides two concrete implementations of methods the new sibling method is derived from the combination of leftrightand parent typicallywe identify the sibling of position as the "otherchild of ' parent howeverif is the rootit has no parentand thus no sibling alsop may be the only child of its parentand thus does not have sibling finallycode fragment provides concrete implementation of the children methodthis method is abstract in the tree class although we have still not specified how the children of node will be storedwe derive generator for the ordered children based upon the implied behavior of abstract methods left and right