class_docstr: Data stored in one DGL server.
  
  In a distributed setting, DGL partitions all data associated with the graph
  (e.g., node and edge features, graph structure, etc.) to multiple partitions,
  each handled by one DGL server. Hence, the ServerState class includes all
  the data associated with a graph partition.
  
  Under some setup, users may want to deploy servers in a heterogeneous way
  -- servers are further divided into special groups for fetching/updating
  node/edge data and for sampling/querying on graph structure respectively.
  In this case, the ServerState can be configured to include only node/edge
  data or graph structure.
  
  Each machine can have multiple server and client processes, but only one
  server is the *master* server while all the others are backup servers. All
  clients and backup servers share the state of the master server via shared
  memory, which means the ServerState class must be serializable and large
  bulk data (e.g., node/edge features) must be stored in NDArray to leverage
  shared memory.
  
  Attributes
  ----------
  kv_store : KVServer
      reference for KVServer
  graph : DGLGraph
      Graph structure of one partition
  total_num_nodes : int
      Total number of nodes
  total_num_edges : int
      Total number of edges
  partition_book : GraphPartitionBook
      Graph Partition book
docstr: Get graph data.
docstr_tok: ["Get","graph","data","."]
code: def graph(self):
      """Get graph data."""
      return self._graph
  
file_path: dgl/python/dgl/distributed/server_state.py
imports: from .._ffi.function import _init_api
label_desc: Use image node_id 5 for calling the ServerState obj's underlying member method code with example usage: obj.graph() and returns: self