code: private static boolean envelopeEqualsEnvelope_(Envelope2D env_a,
  			Envelope2D env_b, double tolerance, ProgressTracker progress_tracker) {
  		return envelopeInfContainsEnvelope_(env_a, env_b, tolerance)
  				&& envelopeInfContainsEnvelope_(env_b, env_a, tolerance);
  	}
docs: Returns true if env_a equals env_b.