old_contents: import pytest
  from poliastro.twobody.mean_elements import get_mean_elements
  
  def test_get_mean_elements_raises_error_if_invalid_body():
      body = "Sun"
  
      with pytest.raises(ValueError) as excinfo:
          get_mean_elements(body)
      assert f"The input body is invalid." in excinfo.exconly()
  
new_contents: import pytest
  
  from poliastro.twobody.mean_elements import get_mean_elements
  
  
  def test_get_mean_elements_raises_error_if_invalid_body():
      body = "Sun"
  
      with pytest.raises(ValueError) as excinfo:
          get_mean_elements(body)
      assert f"The input body '{body}' is invalid." in excinfo.exconly()
  
subject: Add test for error check