'Download a log file from RDS
:type instance_id: str
:param instance_id: The identifier of a DBInstance.
:type log_file_name: str
:param log_file_name: The name of the log file to retrieve
:type marker: str
:param marker: A marker returned from a previous call to this method, or 0 to indicate the start of file. If
no marker is specified, this will fetch log lines from the end of file instead.
:type number_of_lines: int
:param marker: The maximium number of lines to be returned.'

def get_log_file(self, dbinstance_id, log_file_name, marker=None, number_of_lines=None, max_records=None):

    params = {'DBInstanceIdentifier': dbinstance_id, 'LogFileName': log_file_name}
    if marker:
        params['Marker'] = marker
    if number_of_lines:
        params['NumberOfLines'] = number_of_lines
    if max_records:
        params['MaxRecords'] = max_records
    logfile = self.get_object('DownloadDBLogFilePortion', params, LogFileObject)
    if logfile:
        logfile.log_filename = log_file_name
        logfile.dbinstance_id = dbinstance_id
    return logfile
