@classmethod
def _getExtra(cls, grows, extraD=False):
    """ provides growing dimension

        :param grows: growing dimension
        :type grows: :obj:`int`
        :param extraD: True if the object grows
        :type extraD: :obj:`bool`
        :returns: growing dimension
        :rtype: :obj:`int`
        """
    if extraD:
        if grows and grows > 1:
            exDim = grows
        else:
            exDim = 1
    else:
        exDim = 0
    return exDim
