Given a tree aTree, returns a boolean telling if the tree is a leaf or not (i.e if it has no children). This function considers that aTree is effectively a tree.
aTree
the tree to consider
if the value is effectively a leaf with no children
Given a tree
aTree, returns a boolean telling if the tree is a leaf or not (i.e if it has no children). This function considers thataTreeis effectively a tree.