docs: public static double poissonPDFm1(double x_plus_1, double lambda) {
      if(Double.isInfinite(lambda)) {
        return 0.;
      }
      if(x_plus_1 > 1) {
        return rawProbability(x_plus_1 - 1, lambda);
      }
      if(lambda > Math.abs(x_plus_1 - 1) * MathUtil.LOG2 * Double.MAX_EXPONENT / 1e-14) {
        return FastMath.exp(-lambda - GammaDistribution.logGamma(x_plus_1));
      }
      else {
        return rawProbability(x_plus_1, lambda) * (x_plus_1 / lambda);
      }
    }