code: def sampleCellsWithinColumns(numCellPairs, cellsPerColumn, numColumns, seed=42):
    
    np.random.seed(seed)
    cellPairs = []
    for i in range(numCellPairs):
      randCol = np.random.randint(numColumns)
      randCells = np.random.choice(np.arange(cellsPerColumn), (2, ), replace=False)
  
      cellsPair = randCol * cellsPerColumn + randCells
      cellPairs.append(cellsPair)
    return cellPairs
docs: Generate indices of cell pairs, each pair of cells are from the same column
    @return cellPairs (list) list of cell pairs