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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def _conn_string_odbc(self, db_key, instance=None, conn_key=None, db_name=None):
        ''' Return a connection string to use with odbc
        '''
        if instance:
            dsn, host, username, password, database, driver = self._get_access_info(instance, db_key, db_name)
        elif conn_key:
            dsn, host, username, password, database, driver = conn_key.split(":")

        conn_str = ''
        if dsn:
            conn_str = 'DSN={};'.format(dsn)

        if driver:
            conn_str += 'DRIVER={};'.format(driver)
        if host:
            conn_str += 'Server={};'.format(host)
        if database:
            conn_str += 'Database={};'.format(database)

        if username:
            conn_str += 'UID={};'.format(username)
        self.log.debug("Connection string (before password) {}".format(conn_str))
        if password:
            conn_str += 'PWD={};'.format(password)
        return conn_str