def get_crystal_family(number):
    """
    Given a spacegroup number, returns a string to identify its
    crystal family (triclinic, monoclinic, ...).

    :param number: the spacegroup number, from 1 to 230
    """
    if not isinstance(number, int):
        raise TypeError('number should be integer')
    if number < 1:
        raise ValueError('number should be >= 1')
    if number <= 2:
        return 'a'
    elif number <= 15:
        return 'm'
    elif number <= 74:
        return 'o'
    elif number <= 142:
        return 't'
    elif number <= 194:
        return 'h'
    elif number <= 230:
        return 'c'
    else:
        raise ValueError('number should be <= 230')
