def describe_replication_groups(ReplicationGroupId=None, MaxRecords=None,
    Marker=None):
    """
    Returns information about a particular replication group. If no identifier is specified, DescribeReplicationGroups returns information about all replication groups.
    See also: AWS API Documentation
    
    
    :example: response = client.describe_replication_groups(
        ReplicationGroupId='string',
        MaxRecords=123,
        Marker='string'
    )
    
    
    :type ReplicationGroupId: string
    :param ReplicationGroupId: The identifier for the replication group to be described. This parameter is not case sensitive.
            If you do not specify this parameter, information about all replication groups is returned.
            

    :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 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 marker returned from a prior request. Use this marker for pagination of results from this operation. 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',
        'ReplicationGroups': [
            {
                'ReplicationGroupId': 'string',
                'Description': 'string',
                'Status': 'string',
                'PendingModifiedValues': {
                    'PrimaryClusterId': 'string',
                    'AutomaticFailoverStatus': 'enabled'|'disabled'
                },
                'MemberClusters': [
                    'string',
                ],
                'NodeGroups': [
                    {
                        'NodeGroupId': 'string',
                        'Status': 'string',
                        'PrimaryEndpoint': {
                            'Address': 'string',
                            'Port': 123
                        },
                        'Slots': 'string',
                        'NodeGroupMembers': [
                            {
                                'CacheClusterId': 'string',
                                'CacheNodeId': 'string',
                                'ReadEndpoint': {
                                    'Address': 'string',
                                    'Port': 123
                                },
                                'PreferredAvailabilityZone': 'string',
                                'CurrentRole': 'string'
                            },
                        ]
                    },
                ],
                'SnapshottingClusterId': 'string',
                'AutomaticFailover': 'enabled'|'disabled'|'enabling'|'disabling',
                'ConfigurationEndpoint': {
                    'Address': 'string',
                    'Port': 123
                },
                'SnapshotRetentionLimit': 123,
                'SnapshotWindow': 'string',
                'ClusterEnabled': True|False,
                'CacheNodeType': 'string'
            },
        ]
    }
    
    
    :returns: 
    Redis versions earlier than 2.8.6.
    Redis (cluster mode disabled):T1 and T2 cache node types. Redis (cluster mode enabled): T1 node types.
    
    """
    pass
