* the range map, or {@code null} otherwise.
   */
  @Nullable Entry<Range<K>, V> getEntry(K key);

  /**
   * Returns the minimal range {@linkplain Range#encloses(Range) enclosing} the ranges in this
   * {@code RangeMap}.
   *
   * @throws NoSuchElementException if this range map is empty
   */
  Range<K> span();

  /**
   * Maps a range to a specified value (optional operation).
   *

        // Mapping already established
        // This is possible when following both superClass -> enclosingClass
        // and enclosingclass -> superClass paths.
        // Since we follow the path of superclass first, enclosing second,
        // superclass mapping should take precedence.
        return;
      }
      // First, check whether var -> arg forms a cycle

  }

  /**
   * Quasi-implementation of {@link ListIterator} that works from a list of elements and a set of
   * features to support (from the enclosing {@link AbstractIteratorTester} instance). Instead of
   * throwing exceptions like {@link NoSuchElementException} at the appropriate times, it throws

  }

  /**
   * Quasi-implementation of {@link ListIterator} that works from a list of elements and a set of
   * features to support (from the enclosing {@link AbstractIteratorTester} instance). Instead of
   * throwing exceptions like {@link NoSuchElementException} at the appropriate times, it throws

    rangeMap.putCoalescing(Range.closedOpen(2, 4), 1); // between
    rangeMap.putCoalescing(Range.closedOpen(9, 14), 0); // different value
    rangeMap.putCoalescing(Range.closedOpen(17, 20), 3); // enclosing

    rangeMap.putCoalescing(Range.closedOpen(22, 23), 4); // disconnected
    rangeMap.putCoalescing(Range.closedOpen(23, 25), 4); // greater than minimum

    // {[-6..-4): 0, [0..1): 1, [1..5): 1, [7..9): 2,

       *   the task and detect whether it has been cancelled.)
       *
       * - ReschedulableCallable has a reference back to its enclosing CustomScheduler. (It needs it
       *   so that it can call getNextSchedule).
       *
       * Maybe there is a way to avoid this cycle. But we think the cycle is safe enough to ignore:

        // Mapping already established
        // This is possible when following both superClass -> enclosingClass
        // and enclosingclass -> superClass paths.
        // Since we follow the path of superclass first, enclosing second,
        // superclass mapping should take precedence.
        return;
      }
      // First, check whether var -> arg forms a cycle

       *   the task and detect whether it has been cancelled.)
       *
       * - ReschedulableCallable has a reference back to its enclosing CustomScheduler. (It needs it
       *   so that it can call getNextSchedule).
       *
       * Maybe there is a way to avoid this cycle. But we think the cycle is safe enough to ignore:

20E2..20E3    ; valid                  ;      ; NV8    # 3.0  COMBINING ENCLOSING SCREEN..COMBINING ENCLOSING KEYCAP
20E4..20EA    ; valid                  ;      ; NV8    # 3.2  COMBINING ENCLOSING UPWARD POINTING TRIANGLE..COMBINING LEFTWARDS ARROW OVERLAY
20EB          ; valid                  ;      ; NV8    # 4.1  COMBINING LONG DOUBLE SOLIDUS OVERLAY