'Promotes a read replica DB instance to a standalone DB
instance.
:type db_instance_identifier: string
:param db_instance_identifier: The DB instance identifier. This value
is stored as a lowercase string.
Constraints:
+ Must be the identifier for an existing read replica DB instance
+ 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
Example: mydbinstance
:type backup_retention_period: integer
:param backup_retention_period:
The number of days to retain automated backups. Setting this parameter
to a positive number enables backups. Setting this parameter to 0
disables automated backups.
Default: 1
Constraints:
+ Must be a value from 0 to 8
:type preferred_backup_window: string
:param preferred_backup_window: The daily time range during which
automated backups are created if automated backups are enabled,
using the `BackupRetentionPeriod` parameter.
Default: A 30-minute window selected at random from an 8-hour block of
time per region. See the Amazon RDS User Guide for the time blocks
for each region from which the default backup windows are assigned.
Constraints: Must be in the format `hh24:mi-hh24:mi`. Times should be
Universal Time Coordinated (UTC). Must not conflict with the
preferred maintenance window. Must be at least 30 minutes.'

def promote_read_replica(self, db_instance_identifier, backup_retention_period=None, preferred_backup_window=None):

    params = {'DBInstanceIdentifier': db_instance_identifier}
    if (backup_retention_period is not None):
        params['BackupRetentionPeriod'] = backup_retention_period
    if (preferred_backup_window is not None):
        params['PreferredBackupWindow'] = preferred_backup_window
    return self._make_request(action='PromoteReadReplica', verb='POST', path='/', params=params)
