'Downloads the last line of the specified log file.
:type db_instance_identifier: string
:param db_instance_identifier:
The customer-assigned name of the DB instance that contains the log
files you want to list.
Constraints:
+ Must contain from 1 to 63 alphanumeric characters or hyphens
+ First character must be a letter
+ Cannot end with a hyphen or contain two consecutive hyphens
:type log_file_name: string
:param log_file_name: The name of the log file to be downloaded.
:type marker: string
:param marker: The pagination token provided in the previous request.
If this parameter is specified the response includes only records
beyond the marker, up to MaxRecords.
:type number_of_lines: integer
:param number_of_lines: The number of lines remaining to be downloaded.'

def download_db_log_file_portion(self, db_instance_identifier, log_file_name, marker=None, number_of_lines=None):

    params = {'DBInstanceIdentifier': db_instance_identifier, 'LogFileName': log_file_name}
    if (marker is not None):
        params['Marker'] = marker
    if (number_of_lines is not None):
        params['NumberOfLines'] = number_of_lines
    return self._make_request(action='DownloadDBLogFilePortion', verb='POST', path='/', params=params)
