contains method

Returns true, if the tree contains value.

bool contains(
T value,
{int compare(T v1, T v2): null}
)

Returns true, if the tree contains value.

If supplied, compare is used to compare value with values already present in the tree. compare must be consistent with the ordering of values already present in this tree, but it may supply a more efficient implementation of the comparison operation for this very invocation of contains.