docstr: get all data nodes in Milvus deployment
docstr_tok: ["get","all","data","nodes","in","Milvus","deployment"]
code: def data_nodes(self):
      """get all data nodes in Milvus deployment"""
      data_nodes = []
      for node in self.nodes:
          if "datanode" == node.get("infos").get("type"):
              data_nodes.append(node)
      return data_nodes
  
file_path: milvus/tests/python_client/common/milvus_sys.py
imports: import ujson
  import json
  from pymilvus.grpc_gen import milvus_pb2
  from pymilvus import connections
label_desc: Use image node_id 7 for calling the MilvusSys obj's underlying member method code with example usage: obj.data_nodes() and returns: data_nodes