Create a new DBInstance.

        :type id: str
        :param id: Unique identifier for the new instance.
                   Must contain 1-63 alphanumeric characters.
                   First character must be a letter.
                   May not end with a hyphen or contain two consecutive hyphens

        :type allocated_storage: int
        :param allocated_storage: Initially allocated storage size, in GBs.
                                  Valid values are [5-1024]

        :type instance_class: str
        :param instance_class: The compute and memory capacity of
                               the DBInstance. Valid values are:

                               * db.m1.small
                               * db.m1.large
                               * db.m1.xlarge
                               * db.m2.xlarge
                               * db.m2.2xlarge
                               * db.m2.4xlarge

        :type engine: str
        :param engine: Name of database engine. Must be MySQL5.1 for now.

        :type master_username: str
        :param master_username: Name of master user for the DBInstance.
                                Must be 1-15 alphanumeric characters, first
                                must be a letter.

        :type master_password: str
        :param master_password: Password of master user for the DBInstance.
                                Must be 4-16 alphanumeric characters.

        :type port: int
        :param port: Port number on which database accepts connections.
                     Valid values [1115-65535].  Defaults to 3306.

        :type db_name: str
        :param db_name: Name of a database to create when the DBInstance
                        is created.  Default is to create no databases.

        :type param_group: str
        :param param_group: Name of DBParameterGroup to associate with
                            this DBInstance.  If no groups are specified
                            no parameter groups will be used.

        :type security_groups: list of str or list of DBSecurityGroup objects
        :param security_groups: List of names of DBSecurityGroup to authorize on
                                this DBInstance.

        :type availability_zone: str
        :param availability_zone: Name of the availability zone to place
                                  DBInstance into.

        :type preferred_maintenance_window: str
        :param preferred_maintenance_window: The weekly time range (in UTC)
                                             during which maintenance can occur.
                                             Default is Sun:05:00-Sun:09:00

        :type backup_retention_period: int
        :param backup_retention_period: The number of days for which automated
                                        backups are retained.  Setting this to
                                        zero disables automated backups.

        :type preferred_backup_window: str
        :param preferred_backup_window: The daily time range during which
                                        automated backups are created (if
                                        enabled).  Must be in h24:mi-hh24:mi
                                        format (UTC).

        :type multi_az: bool
        :param multi_az: If True, specifies the DB Instance will be
                         deployed in multiple availability zones.

        :type engine_version: str
        :param engine_version: Version number of the database engine to use.

        :type auto_minor_version_upgrade: bool
        :param auto_minor_version_upgrade: Indicates that minor engine
                                           upgrades will be applied
                                           automatically to the Read Replica
                                           during the maintenance window.
                                           Default is True.

        :rtype: :class:`boto.rds.dbinstance.DBInstance`
        :return: The new db instance.

def create_dbinstance(self, id, allocated_storage, instance_class,
                          master_username, master_password, port=3306,
                          engine='MySQL5.1', db_name=None, param_group=None,
                          security_groups=None, availability_zone=None,
                          preferred_maintenance_window=None,
                          backup_retention_period=None,
                          preferred_backup_window=None,
                          multi_az=False,
                          engine_version=None,
                          auto_minor_version_upgrade=True):
        """
        Create a new DBInstance.

        :type id: str
        :param id: Unique identifier for the new instance.
                   Must contain 1-63 alphanumeric characters.
                   First character must be a letter.
                   May not end with a hyphen or contain two consecutive hyphens

        :type allocated_storage: int
        :param allocated_storage: Initially allocated storage size, in GBs.
                                  Valid values are [5-1024]

        :type instance_class: str
        :param instance_class: The compute and memory capacity of
                               the DBInstance. Valid values are:

                               * db.m1.small
                               * db.m1.large
                               * db.m1.xlarge
                               * db.m2.xlarge
                               * db.m2.2xlarge
                               * db.m2.4xlarge

        :type engine: str
        :param engine: Name of database engine. Must be MySQL5.1 for now.

        :type master_username: str
        :param master_username: Name of master user for the DBInstance.
                                Must be 1-15 alphanumeric characters, first
                                must be a letter.

        :type master_password: str
        :param master_password: Password of master user for the DBInstance.
                                Must be 4-16 alphanumeric characters.

        :type port: int
        :param port: Port number on which database accepts connections.
                     Valid values [1115-65535].  Defaults to 3306.

        :type db_name: str
        :param db_name: Name of a database to create when the DBInstance
                        is created.  Default is to create no databases.

        :type param_group: str
        :param param_group: Name of DBParameterGroup to associate with
                            this DBInstance.  If no groups are specified
                            no parameter groups will be used.

        :type security_groups: list of str or list of DBSecurityGroup objects
        :param security_groups: List of names of DBSecurityGroup to authorize on
                                this DBInstance.

        :type availability_zone: str
        :param availability_zone: Name of the availability zone to place
                                  DBInstance into.

        :type preferred_maintenance_window: str
        :param preferred_maintenance_window: The weekly time range (in UTC)
                                             during which maintenance can occur.
                                             Default is Sun:05:00-Sun:09:00

        :type backup_retention_period: int
        :param backup_retention_period: The number of days for which automated
                                        backups are retained.  Setting this to
                                        zero disables automated backups.

        :type preferred_backup_window: str
        :param preferred_backup_window: The daily time range during which
                                        automated backups are created (if
                                        enabled).  Must be in h24:mi-hh24:mi
                                        format (UTC).

        :type multi_az: bool
        :param multi_az: If True, specifies the DB Instance will be
                         deployed in multiple availability zones.

        :type engine_version: str
        :param engine_version: Version number of the database engine to use.

        :type auto_minor_version_upgrade: bool
        :param auto_minor_version_upgrade: Indicates that minor engine
                                           upgrades will be applied
                                           automatically to the Read Replica
                                           during the maintenance window.
                                           Default is True.

        :rtype: :class:`boto.rds.dbinstance.DBInstance`
        :return: The new db instance.
        """
        params = {'DBInstanceIdentifier': id,
                  'AllocatedStorage': allocated_storage,
                  'DBInstanceClass': instance_class,
                  'Engine': engine,
                  'MasterUsername': master_username,
                  'MasterUserPassword': master_password,
                  'Port': port,
                  'MultiAZ': str(multi_az).lower(),
                  'AutoMinorVersionUpgrade':
                      str(auto_minor_version_upgrade).lower()}
        if db_name:
            params['DBName'] = db_name
        if param_group:
            params['DBParameterGroupName'] = param_group
        if security_groups:
            l = []
            for group in security_groups:
                if isinstance(group, DBSecurityGroup):
                    l.append(group.name)
                else:
                    l.append(group)
            self.build_list_params(params, l, 'DBSecurityGroups.member')
        if availability_zone:
            params['AvailabilityZone'] = availability_zone
        if preferred_maintenance_window:
            params['PreferredMaintenanceWindow'] = preferred_maintenance_window
        if backup_retention_period is not None:
            params['BackupRetentionPeriod'] = backup_retention_period
        if preferred_backup_window:
            params['PreferredBackupWindow'] = preferred_backup_window
        if engine_version:
            params['EngineVersion'] = engine_version

        return self.get_object('CreateDBInstance', params, DBInstance)