diff --git a/masque/builder/builder.py b/masque/builder/builder.py
index 1a8c075..9b4931c 100644
--- a/masque/builder/builder.py
+++ b/masque/builder/builder.py
@@ -1,8 +1,7 @@
-from typing import Self, Sequence, MutableMapping, Mapping
+from typing import Self, Sequence, Mapping
 import copy
 import logging
 
-import numpy
 from numpy import pi
 from numpy.typing import ArrayLike
 
diff --git a/masque/builder/pather.py b/masque/builder/pather.py
index 1064df2..b17d70f 100644
--- a/masque/builder/pather.py
+++ b/masque/builder/pather.py
@@ -7,7 +7,6 @@ from numpy import pi
 from numpy.typing import ArrayLike
 
 from ..pattern import Pattern
-from ..ref import Ref
 from ..library import ILibrary
 from ..error import PortError, BuildError
 from ..ports import PortList, Port
diff --git a/masque/file/dxf.py b/masque/file/dxf.py
index 110129c..a2e9b60 100644
--- a/masque/file/dxf.py
+++ b/masque/file/dxf.py
@@ -73,7 +73,7 @@ def write(
         stream: Stream object to write to.
     """
     #TODO consider supporting DXF arcs?
-    if not isinstance(library, Library):
+    if not isinstance(library, ILibraryView):
         if isinstance(library, dict):
             library = LibraryView(library)
         else:
diff --git a/masque/library.py b/masque/library.py
index 6940613..4ae144c 100644
--- a/masque/library.py
+++ b/masque/library.py
@@ -496,7 +496,6 @@ class ILibrary(ILibraryView, MutableMapping[str, 'Pattern'], metaclass=ABCMeta):
         self.rename(self.top(), name, move_references=True)
         return self
 
-
     def move_references(self, old_target: str, new_target: str) -> Self:
         """
         Change all references pointing at `old_target` into references pointing at `new_target`.
diff --git a/masque/pattern.py b/masque/pattern.py
index e1ba0ed..801f262 100644
--- a/masque/pattern.py
+++ b/masque/pattern.py
@@ -585,7 +585,6 @@ class Pattern(PortList, AnnotatableImpl, Mirrorable):
         self.labels.append(Label(*args, **kwargs))
         return self
 
-
     def flatten(
             self,
             library: Mapping[str, 'Pattern'],
diff --git a/masque/traits/layerable.py b/masque/traits/layerable.py
index ec62096..2ccd65e 100644
--- a/masque/traits/layerable.py
+++ b/masque/traits/layerable.py
@@ -12,6 +12,7 @@ class Layerable(metaclass=ABCMeta):
     Trait class for all layerable entities
     """
     __slots__ = ()
+
     #
     # Properties
     #