'Args:
ds(DataFlow): input DataFlow.
num(int): number of dataflow points to print.
name(str, optional): name to identify this DataFlow.'

def __init__(self, ds, num=1, label=None, name=None):

    super(PrintData, self).__init__(ds)
    self.num = num
    if label:
        log_deprecated('PrintData(label,    ...', 'Use    PrintData(name,    ...    instead.')
        self.name = label
    else:
        self.name = name
    self.cnt = 0
