docs: public static ZMatrixRMaj pivotMatrix(ZMatrixRMaj ret, int pivots[], int numPivots, boolean transposed ) {
  
          if( ret == null ) {
              ret = new ZMatrixRMaj(numPivots, numPivots);
          } else {
              if( ret.numCols != numPivots || ret.numRows != numPivots )
                  throw new IllegalArgumentException("Unexpected matrix dimension");
              CommonOps_ZDRM.fill(ret, 0,0);
          }
  
          if( transposed ) {
              for( int i = 0; i < numPivots; i++ ) {
                  ret.set(pivots[i],i,1,0);
              }
          } else {
              for( int i = 0; i < numPivots; i++ ) {
                  ret.set(i,pivots[i],1,0);
              }
          }
  
          return ret;
      }