def getindices_StreakingData(list_ParentGrain_transforms):
    """read list_ParentGrain_transforms and return for each element
    the positions indices to extract date for straeking plot

    # assuming that first elements are in correct order and contiguous ...

    >>> getindices_StreakingData([[0, 132, 'slipsystem'], [1, 1, 'parametric']])
    >>> {0:[0,132],1:None}

    >>> getindices_StreakingData([[0,15,'parametric'],[1,132,'slipsystem'],
    [2,1,'parametric'],[3,500,'slipsystem']])
    >>> {0: None, 1: [15, 147], 2: None, 3: [148, 648]}


    """
    nbparentgrains = len(list_ParentGrain_transforms)
    dictindices = {}
    accum_nb = 0
    for k in range(nbparentgrains):
        gindex, nbtransforms, transform_type = list_ParentGrain_transforms[k]
        if transform_type == 'slipsystem':
            dictindices[gindex] = [accum_nb, accum_nb + nbtransforms]
        if transform_type == 'parametric':
            dictindices[gindex] = None
        accum_nb += nbtransforms
    return dictindices
