Provide a way to change default HL7 parameter if you want to subclass
        :param header_segment: Expected segment, for HL7, it's MSH
        :param segment_len: Expected length of segment, for HL7, it's 3
        :param separator_count: Expected count of separators, for HL7, it's 5
        :return: None

def changeDefaultMessageConst(self, header_segment, segment_len, separator_count):
        """
        Provide a way to change default HL7 parameter if you want to subclass
        :param header_segment: Expected segment, for HL7, it's MSH
        :param segment_len: Expected length of segment, for HL7, it's 3
        :param separator_count: Expected count of separators, for HL7, it's 5
        :return: None
        """
        self.header_segment = header_segment
        self.segment_len = segment_len
        self.separator_count = separator_count