Returns a spark string from given iterable of ints.

def spark_string(ints):
    """Returns a spark string from given iterable of ints."""
    ticks = u'▁▂▃▅▆▇'
    ints = [i for i in ints if type(i) == int]
    if len(ints) == 0:
        return ""
    step = (max(ints) / float(len(ticks) - 1)) or 1
    return u''.join(
        ticks[int(round(i / step))] if type(i) == int else u'.' for i in ints)