def METHOD_NAME(self, cellPointIdsList):
    '''convert a list of numpy arrays defining each cell into a flat array defining cells. 
    This function is the inverse of vmtk.meshtonumpy._ConvertFlatCellsArrayToList(cells, cellLocations)
    arguments: 
        - cellPointIdsList: list of numpy arrays (in same order defined in cells), where each array contains 
                            the cellPointIds for that specific cell. Note: array lengths are not constant, 
                            each cell can have a different number of constituent points.
    returns:
        - cells: 1D array of format [npointsCell1, cell1PointId_1, .., cell1PointId_npointsCell1, 
                                    npointsCell2, cell2PointId_1, .., cell2PointId_npointsCell2, 
                                    ... 
                                    npointsCell(nCells), cell(nCells)PointId_1, .. cell(nCells)PointId_npointsCell(nCells)]
        - cellLocations: flat array of size = nCells. each element in the array defines starts a new cell 
                        (a location of npointCellFoo) in the cells array
    '''
    cellArrayList = []
    cellLocationsList = [np.array([0])]
    cellIndex = 0
    for cellPointIdArray in cellPointIdsList:
        numPointsInArray = cellPointIdArray.size
        cellArray = np.concatenate((np.array([numPointsInArray]), cellPointIdArray))
        cellArrayList.append(cellArray)
        cellIndex += cellArray.size
        cellLocationsList.append(np.array([cellIndex]))
    cellLocations = np.concatenate(cellLocationsList[:-1])
    cells = np.concatenate(cellArrayList)
    return cells, cellLocations