diff --git a/tests/test_components/test_parameter_perturbation.py b/tests/test_components/test_parameter_perturbation.py
index 819a0aebb4..2f6d850f6e 100644
--- a/tests/test_components/test_parameter_perturbation.py
+++ b/tests/test_components/test_parameter_perturbation.py
@@ -6,10 +6,7 @@
 import pytest
 import tidy3d as td
 
-from ..utils import cartesian_to_unstructured
-
-from ..utils import assert_log_level, AssertLogLevel
-from ..utils import log_capture  # noqa: F401
+from ..utils import cartesian_to_unstructured, AssertLogLevel
 
 sp_arr = td.SpatialDataArray(300 * np.ones((2, 2, 2)), coords=dict(x=[1, 2], y=[3, 4], z=[5, 6]))
 sp_arr_u = cartesian_to_unstructured(sp_arr)
diff --git a/tests/test_components/test_perturbation_medium.py b/tests/test_components/test_perturbation_medium.py
index b83d6af5b4..34f6f60527 100644
--- a/tests/test_components/test_perturbation_medium.py
+++ b/tests/test_components/test_perturbation_medium.py
@@ -5,7 +5,6 @@
 import pydantic.v1 as pydantic
 import tidy3d as td
 from ..utils import AssertLogLevel, cartesian_to_unstructured
-from ..utils import log_capture  # noqa: F401
 
 
 @pytest.mark.parametrize("unstructured", [False, True])
diff --git a/tidy3d/__init__.py b/tidy3d/__init__.py
index 264a83ac15..a527535740 100644
--- a/tidy3d/__init__.py
+++ b/tidy3d/__init__.py
@@ -190,11 +190,11 @@
 from .components.parameter_perturbation import (
     CustomChargePerturbation,
     CustomHeatPerturbation,
+    IndexPerturbation,
     LinearChargePerturbation,
     LinearHeatPerturbation,
     ParameterPerturbation,
     PermittivityPerturbation,
-    IndexPerturbation,
 )
 
 # run time spec
diff --git a/tidy3d/components/medium.py b/tidy3d/components/medium.py
index 18514abe3e..e3d7996ac7 100644
--- a/tidy3d/components/medium.py
+++ b/tidy3d/components/medium.py
@@ -49,7 +49,11 @@
 from .geometry.base import Geometry
 from .grid.grid import Coords, Grid
 from .heat_spec import HeatSpecType
-from .parameter_perturbation import ParameterPerturbation, PermittivityPerturbation, IndexPerturbation
+from .parameter_perturbation import (
+    IndexPerturbation,
+    ParameterPerturbation,
+    PermittivityPerturbation,
+)
 from .time_modulation import ModulationSpec
 from .transformation import RotationType
 from .types import (
@@ -65,7 +69,7 @@
     PoleAndResidue,
     TensorReal,
 )
-from .validators import validate_name_str, validate_parameter_perturbation
+from .validators import _warn_potential_error, validate_name_str, validate_parameter_perturbation
 from .viz import add_ax_if_none
 
 # evaluate frequency as this number (Hz) if inf
diff --git a/tidy3d/components/parameter_perturbation.py b/tidy3d/components/parameter_perturbation.py
index 953ae3a938..e68c1f64dc 100644
--- a/tidy3d/components/parameter_perturbation.py
+++ b/tidy3d/components/parameter_perturbation.py
@@ -4,7 +4,7 @@
 
 import functools
 from abc import ABC, abstractmethod
-from typing import Callable, List, Tuple, Union, Optional
+from typing import Callable, List, Optional, Tuple, Union
 
 import matplotlib.pyplot as plt
 import numpy as np
@@ -13,7 +13,7 @@
 from ..components.data.validators import validate_no_nans
 from ..components.types import TYPE_TAG_STR, ArrayLike, Ax, Complex, FieldVal, InterpMethod
 from ..components.viz import add_ax_if_none
-from ..constants import CMCUBE, KELVIN, PERCMCUBE, inf
+from ..constants import CMCUBE, EPSILON_0, KELVIN, PERCMCUBE, inf
 from ..exceptions import DataError
 from ..log import log
 from .base import Tidy3dBaseModel, cached_property