def describe_db_instances(DBInstanceIdentifier=None, Filters=None,
    MaxRecords=None, Marker=None):
    """
    Returns information about provisioned RDS instances. This API supports pagination.
    See also: AWS API Documentation
    
    Examples
    This example lists settings for the specified DB instance.
    Expected Output:
    
    :example: response = client.describe_db_instances(
        DBInstanceIdentifier='string',
        Filters=[
            {
                'Name': 'string',
                'Values': [
                    'string',
                ]
            },
        ],
        MaxRecords=123,
        Marker='string'
    )
    
    
    :type DBInstanceIdentifier: string
    :param DBInstanceIdentifier: The user-supplied instance identifier. If this parameter is specified, information from only the specific DB instance is returned. This parameter isn't case-sensitive.
            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 Filters: list
    :param Filters: A filter that specifies one or more DB instances to describe.
            Supported filters:
            db-cluster-id - Accepts DB cluster identifiers and DB cluster Amazon Resource Names (ARNs). The results list will only include information about the DB instances associated with the DB Clusters identified by these ARNs.
            db-instance-id - Accepts DB instance identifiers and DB instance Amazon Resource Names (ARNs). The results list will only include information about the DB instances identified by these ARNs.
            (dict) --This type is not currently supported.
            Name (string) -- [REQUIRED]This parameter is not currently supported.
            Values (list) -- [REQUIRED]This parameter is not currently supported.
            (string) --
            
            

    :type MaxRecords: integer
    :param MaxRecords: The maximum number of records to include in the response. If more records exist than the specified MaxRecords value, a pagination token called a marker is included in the response so that the remaining results can be retrieved.
            Default: 100
            Constraints: Minimum 20, maximum 100.
            

    :type Marker: string
    :param Marker: An optional pagination token provided by a previous DescribeDBInstances request. If this parameter is specified, the response includes only records beyond the marker, up to the value specified by MaxRecords .

    :rtype: dict
    :return: {
        'Marker': 'string',
        'DBInstances': [
            {
                'DBInstanceIdentifier': 'string',
                'DBInstanceClass': 'string',
                'Engine': 'string',
                'DBInstanceStatus': 'string',
                'MasterUsername': 'string',
                'DBName': 'string',
                'Endpoint': {
                    'Address': 'string',
                    'Port': 123,
                    'HostedZoneId': 'string'
                },
                'AllocatedStorage': 123,
                'InstanceCreateTime': datetime(2015, 1, 1),
                'PreferredBackupWindow': 'string',
                'BackupRetentionPeriod': 123,
                'DBSecurityGroups': [
                    {
                        'DBSecurityGroupName': 'string',
                        'Status': 'string'
                    },
                ],
                'VpcSecurityGroups': [
                    {
                        'VpcSecurityGroupId': 'string',
                        'Status': 'string'
                    },
                ],
                'DBParameterGroups': [
                    {
                        'DBParameterGroupName': 'string',
                        'ParameterApplyStatus': 'string'
                    },
                ],
                'AvailabilityZone': 'string',
                'DBSubnetGroup': {
                    'DBSubnetGroupName': 'string',
                    'DBSubnetGroupDescription': 'string',
                    'VpcId': 'string',
                    'SubnetGroupStatus': 'string',
                    'Subnets': [
                        {
                            'SubnetIdentifier': 'string',
                            'SubnetAvailabilityZone': {
                                'Name': 'string'
                            },
                            'SubnetStatus': 'string'
                        },
                    ],
                    'DBSubnetGroupArn': 'string'
                },
                'PreferredMaintenanceWindow': 'string',
                'PendingModifiedValues': {
                    'DBInstanceClass': 'string',
                    'AllocatedStorage': 123,
                    'MasterUserPassword': 'string',
                    'Port': 123,
                    'BackupRetentionPeriod': 123,
                    'MultiAZ': True|False,
                    'EngineVersion': 'string',
                    'LicenseModel': 'string',
                    'Iops': 123,
                    'DBInstanceIdentifier': 'string',
                    'StorageType': 'string',
                    'CACertificateIdentifier': 'string',
                    'DBSubnetGroupName': 'string'
                },
                'LatestRestorableTime': datetime(2015, 1, 1),
                'MultiAZ': True|False,
                'EngineVersion': 'string',
                'AutoMinorVersionUpgrade': True|False,
                'ReadReplicaSourceDBInstanceIdentifier': 'string',
                'ReadReplicaDBInstanceIdentifiers': [
                    'string',
                ],
                'ReadReplicaDBClusterIdentifiers': [
                    'string',
                ],
                'LicenseModel': 'string',
                'Iops': 123,
                'OptionGroupMemberships': [
                    {
                        'OptionGroupName': 'string',
                        'Status': 'string'
                    },
                ],
                'CharacterSetName': 'string',
                'SecondaryAvailabilityZone': 'string',
                'PubliclyAccessible': True|False,
                'StatusInfos': [
                    {
                        'StatusType': 'string',
                        'Normal': True|False,
                        'Status': 'string',
                        'Message': 'string'
                    },
                ],
                'StorageType': 'string',
                'TdeCredentialArn': 'string',
                'DbInstancePort': 123,
                'DBClusterIdentifier': 'string',
                'StorageEncrypted': True|False,
                'KmsKeyId': 'string',
                'DbiResourceId': 'string',
                'CACertificateIdentifier': 'string',
                'DomainMemberships': [
                    {
                        'Domain': 'string',
                        'Status': 'string',
                        'FQDN': 'string',
                        'IAMRoleName': 'string'
                    },
                ],
                'CopyTagsToSnapshot': True|False,
                'MonitoringInterval': 123,
                'EnhancedMonitoringResourceArn': 'string',
                'MonitoringRoleArn': 'string',
                'PromotionTier': 123,
                'DBInstanceArn': 'string',
                'Timezone': 'string',
                'IAMDatabaseAuthenticationEnabled': True|False
            },
        ]
    }
    
    
    :returns: 
    CreateDBInstance
    DeleteDBInstance
    ModifyDBInstance
    
    """
    pass
