code: def test_default_signature_assignment():
      expected_signature = {
          "inputs": '[{"type": "string", "required": true}]',
          "outputs": '[{"type": "tensor", "tensor-spec": {"dtype": "float64", "shape": [-1]}}]',
          "params": None,
      }
  
      default_signature = (
          mlflow.sentence_transformers._get_default_signature()
      )
  
      assert default_signature.to_dict() == expected_signature
  
imports: import json
  import os
  from unittest import mock
  import numpy
  import pandas
  import pytest
  import yaml
  from pyspark.sql import SparkSession
  from pyspark.sql.types import ArrayType, DoubleType
  from sentence_transformers import SentenceTransformer
  import mlflow
  import mlflow.pyfunc.scoring_server
  import mlflow.sentence_transformers
  from mlflow import pyfunc
  from mlflow.exceptions import MlflowException
  from mlflow.models import Model, infer_signature
  from mlflow.models.utils import _read_example
  from mlflow.store.artifact.s3_artifact_repo import S3ArtifactRepository
  from mlflow.utils.environment import _mlflow_conda_env
  from tests.helper_functions import _assert_pip_requirements, _compare_logged_code_paths, _mlflow_major_version_string, assert_register_model_called_with_local_model_path, pyfunc_serve_and_score_model
label_desc: Use image node_id 16 for calling a global function with example usage: test_default_signature_assignment() without return types