diff --git a/src/wireviz/DataClasses.py b/src/wireviz/DataClasses.py
index a0addbd..302b121 100644
--- a/src/wireviz/DataClasses.py
+++ b/src/wireviz/DataClasses.py
@@ -43,7 +43,7 @@ class Image:
     caption: Optional[MultilineHypertext] = None
     # See also HTML doc at https://graphviz.org/doc/info/shapes.html#html
 
-    def __post_init__(self):
+    def __post_init__(self) -> None:
 
         if self.fixedsize is None:
             # Default True if any dimension specified unless self.scale also is specified.
diff --git a/src/wireviz/Harness.py b/src/wireviz/Harness.py
index 1791ea4..3a39881 100644
--- a/src/wireviz/Harness.py
+++ b/src/wireviz/Harness.py
@@ -342,7 +342,7 @@ class Harness:
         return data.read()
 
     @property
-    def svg(self):
+    def svg(self) -> str:
         graph = self.create_graph()
         return embed_svg_images(graph.pipe(format='svg').decode('utf-8'), Path.cwd())
 
diff --git a/src/wireviz/svgembed.py b/src/wireviz/svgembed.py
index ea802ca..1ada421 100644
--- a/src/wireviz/svgembed.py
+++ b/src/wireviz/svgembed.py
@@ -8,7 +8,7 @@ from typing import Union
 
 mime_subtype_replacements = {'jpg': 'jpeg', 'tif': 'tiff'}
 
-def embed_svg_images(svg_in: str, base_path: Path):
+def embed_svg_images(svg_in: str, base_path: Union[str, Path] = Path.cwd()) -> str:
     # first, find any image references in SVG data, and cache the respective base64-encoded image
     images_b64 = {}  # cache of base64-encoded images
     re_xlink=re.compile(r'xlink:href="(?P<URL>.*?)"', re.IGNORECASE)
@@ -16,7 +16,6 @@ def embed_svg_images(svg_in: str, base_path: Path):
         imgurl = xlink.group('URL')
         if not imgurl in images_b64:  # only encode/cache every unique URL once
             imgurl_abs = (Path(base_path) / imgurl).resolve()
-
             images_b64[imgurl] = base64.b64encode(imgurl_abs.read_bytes()).decode('utf-8')
     # second, replace links with the base64-encoded data
     svg_out = svg_in
@@ -26,14 +25,14 @@ def embed_svg_images(svg_in: str, base_path: Path):
     return svg_out
 
 
-def get_mime_subtype(filename: Union[str, Path]):
+def get_mime_subtype(filename: Union[str, Path]) -> str:
     mime_subtype = Path(filename).suffix.lstrip('.').lower()
     if mime_subtype in mime_subtype_replacements:
         mime_subtype = mime_subtype_replacements[mime_subtype]
     return mime_subtype
 
 
-def embed_svg_images_file(filename_in: Union[str, Path], overwrite: bool = True):
+def embed_svg_images_file(filename_in: Union[str, Path], overwrite: bool = True) -> None:
     filename_in = Path(filename_in).resolve()
     filename_out = filename_in.with_suffix('.b64.svg')
     filename_out.write_text(embed_svg_images(filename_in.read_text(), filename_in.parent))