code: def test_update_model_cost_via_completion():
      try:
          response = litellm.completion(
              model="gpt-3.5-turbo",
              messages=[
                  {"role": "user", "content": "Hey, how's it going?"}
              ],
              input_cost_per_token=0.3,
              output_cost_per_token=0.4,
          )
          print(
              f"litellm.model_cost for gpt-3.5-turbo: {litellm.model_cost['gpt-3.5-turbo']}"
          )
          assert (
              litellm.model_cost["gpt-3.5-turbo"][
                  "input_cost_per_token"
              ]
              == 0.3
          )
          assert (
              litellm.model_cost["gpt-3.5-turbo"][
                  "output_cost_per_token"
              ]
              == 0.4
          )
      except Exception as e:
          pytest.fail(f"An error occurred: {e}")
  
imports: import sys, os
  import traceback
  import pytest
  import litellm
label_desc: Use image node_id 3 for calling a global function with example usage: test_update_model_cost_via_completion() without return types