docs: private static boolean parallelSideEffect(
              final double pXA, final double pYA, final double pXB, final double pYB,
              final double pXC, final double pYC, final double pXD, final double pYD,
              final PointL pIntersection
      ) {
          if (pXA == pXB) {
              return parallelSideEffectSameX(pXA, pYA, pXB, pYB, pXC, pYC, pXD, pYD, pIntersection);
          }
          if (pXC == pXD) {
              return parallelSideEffectSameX(pXC, pYC, pXD, pYD, pXA, pYA, pXB, pYB, pIntersection);
          }
          // formula like "y = k*x + b"
          final double k1 = (pYB - pYA) / (pXB - pXA);
          final double k2 = (pYD - pYC) / (pXD - pXC);
          if (k1 != k2) { // not parallel
              return false;
          }
          final double b1 = pYA - k1 * pXA;
          final double b2 = pYC - k2 * pXC;
          if (b1 != b2) { // strictly parallel, no overlap
              return false;
          }
          final double xi = middle(pXA, pXB, pXC, pXD);
          final double yi = middle(pYA, pYB, pYC, pYD);
          return check(pXA, pYA, pXB, pYB, pXC, pYC, pXD, pYD, pIntersection, xi, yi);
      }