* must be well-behaved with respect to {@link Object#equals} and {@link Object#hashCode}.
   *
   * @param left the map to treat as the "left" map for purposes of comparison
   * @param right the map to treat as the "right" map for purposes of comparison
   * @param valueEquivalence the equivalence relationship to use to compare values
   * @return the difference between the two maps
   * @since 10.0