Read from the MSH (Message Header) the separators used to separate the pieces
        of data
        Ex: In the message
        MSH|^~\&|OF|Chemistry|ORT||200309060825||ORU^R01^ORU_R01|msgOF105|T|2.5|123||||USA||EN

        The values separator are ^~\&|

        See HL7 Chapter 2

def extractSeparators(self, hl7dict, msg):
        """ Read from the MSH (Message Header) the separators used to separate the pieces
        of data
        Ex: In the message
        MSH|^~\&|OF|Chemistry|ORT||200309060825||ORU^R01^ORU_R01|msgOF105|T|2.5|123||||USA||EN

        The values separator are ^~\&|

        See HL7 Chapter 2

        """
        assert msg[:self.segment_len] == self.header_segment, \
            "Message MUST start with the %s segment : Here %s" % (self.header_segment, msg[:self.segment_len])
        hl7dict.separators = msg[self.segment_len:self.segment_len+self.separator_count]