def get_column(data, header):   #new
    """
        Features:
            Get the data under a specific header from the dataset.
        Parameters:
            data: List. The whole dataset.
            header: String. The header of the data that want to get.
        Returns:
            List of string. The data want to get.
    """
    headers = data[0]
    flag = 0    # to get the index of the header.
    for index in range(len(headers)):
        if headers[index] == header:
            flag = index
    result = [line[flag] for line in data[1:]]
    return result