docstr: Add a Network Node Peer
docstr_tok: ["Add","a","Network","Node","Peer"]
code: def add_peer(
      self,
      context: AuthedServiceContext,
      peer: NodePeer,
      challenge: bytes,
      self_node_route: NodeRoute,
      verify_key: SyftVerifyKey,
  ) -> Union[bytes, SyftError]:
      """Add a Network Node Peer"""
      # Using the verify_key of the peer to verify the signature
      # It is also our single source of truth for the peer
      if peer.verify_key != context.credentials:
          return SyftError(
              message=(
                  f"The {type(peer)}.verify_key: "
                  f"{peer.verify_key} does not match the signature of the message"
              )
          )
  
      if verify_key != context.node.verify_key:
          return SyftError(
              message="verify_key does not match the remote node's verify_key for add_peer"
          )
  
      try:
          remote_client: SyftClient = peer.client_with_context(
              context=context
          )
          random_challenge = secrets.token_bytes(16)
          remote_res = remote_client.api.services.network.ping(
              challenge=random_challenge
          )
      except Exception as e:
          return SyftError(
              message="Remote Peer cannot ping peer:" + str(e)
          )
  
      if isinstance(remote_res, SyftError):
          return remote_res
  
      challenge_signature = remote_res
  
      # Verifying if the challenge is valid
      try:
          peer.verify_key.verify_key.verify(
              random_challenge, challenge_signature
          )
      except Exception as e:
          return SyftError(message=str(e))
  
      result = self.stash.update_peer(context.node.verify_key, peer)
      if result.is_err():
          return SyftError(message=str(result.err()))
  
      # this way they can match up who we are with who they think we are
      # Sending a signed messages for the peer to verify
      self_node_peer = self_node_route.validate_with_context(
          context=context
      )
  
      if isinstance(self_node_peer, SyftError):
          return self_node_peer
  
      # Q,TODO: Should the returned node peer also be signed
      # as the challenge is already signed
  
      challenge_signature = context.node.signing_key.signing_key.sign(
          challenge
      ).signature
  
      return [challenge_signature, self_node_peer]
  
imports: import secrets
  from typing import Any
  from typing import Callable
  from typing import List
  from typing import Optional
  from typing import Union
  from result import Result
  from ...abstract_node import NodeType
  from ...client.client import HTTPConnection
  from ...client.client import PythonConnection
  from ...client.client import SyftClient
  from ...node.credentials import SyftVerifyKey
  from ...node.worker_settings import WorkerSettings
  from ...serde.serializable import serializable
  from ...service.settings.settings import NodeSettingsV2
  from ...store.document_store import BaseUIDStoreStash
  from ...store.document_store import DocumentStore
  from ...store.document_store import PartitionKey
  from ...store.document_store import PartitionSettings
  from ...store.document_store import QueryKeys
  from ...types.grid_url import GridURL
  from ...types.transforms import TransformContext
  from ...types.transforms import keep
  from ...types.transforms import transform
  from ...types.transforms import transform_method
  from ...util.telemetry import instrument
  from ..context import AuthedServiceContext
  from ..data_subject.data_subject import NamePartitionKey
  from ..metadata.node_metadata import NodeMetadataV3
  from ..response import SyftError
  from ..response import SyftSuccess
  from ..service import AbstractService
  from ..service import SERVICE_TO_TYPES
  from ..service import TYPE_TO_SERVICE
  from ..service import service_method
  from ..user.user_roles import GUEST_ROLE_LEVEL
  from ..warnings import CRUDWarning
  from .node_peer import NodePeer
  from .routes import HTTPNodeRoute
  from .routes import NodeRoute
  from .routes import PythonNodeRoute
label_desc: Use image node_id 3 for calling the NetworkService obj's underlying member method code with example usage: obj.add_peer(context, peer, challenge, _node_route, verify_key) and returns: list, SyftError, SyftError, remote_res, SyftError, self_node_peer, SyftError, SyftError