diff --git a/src/caosdb/utils/plantuml.py b/src/caosdb/utils/plantuml.py
index 2cc1bb53e50aca7b26dc2ade423f010f43f6a774..0c7936a98e27ec020659d9f7042cd05a9084ef4b 100644
--- a/src/caosdb/utils/plantuml.py
+++ b/src/caosdb/utils/plantuml.py
@@ -168,8 +168,6 @@ hide circle\n
     else:
         raise ValueError("Unknown style.")
 
-    
-
     if add_properties:
         result += "package Properties #DDDDDD {\n"
         for p in properties:
@@ -293,7 +291,7 @@ def retrieve_substructure(start_record_types, depth, result_id_set=None, result_
             if is_reference(prop.datatype) and prop.datatype != db.FILE and depth > 0:
                 rt = db.RecordType(name=get_referenced_recordtype(prop.datatype)).retrieve()
                 retrieve_substructure([rt], depth-1, result_id_set, result_container, False)
-                
+
             # TODO: clean up this hack
             # TODO: make it also work for files
             if is_reference(prop.datatype) and prop.value is not None:
@@ -358,13 +356,13 @@ def to_graphics(recordtypes: list[db.Entity], filename: str,
 
     if output_dirname is None:
         output_dirname = os.getcwd()
-        
+
     allowed_formats = [
         "tpng", "tsvg", "teps", "tpdf", "tvdx", "txmi",
         "tscxml", "thtml", "ttxt", "tutxt", "tlatex", "tlatex:nopreamble"]
 
     with tempfile.TemporaryDirectory() as td:
-        
+
         pu_filename = os.path.join(td, filename + ".pu")
         with open(pu_filename, "w") as pu_file:
             pu_file.write(pu)
@@ -373,7 +371,7 @@ def to_graphics(recordtypes: list[db.Entity], filename: str,
             extension = format[1:]
             if ":" in extension:
                 extension = extension[:extension.index(":")]
-                
+
             if format not in allowed_formats:
                 raise RuntimeError("Format not allowed.")
             cmd = "plantuml -{} {}".format(format, pu_filename)
@@ -381,6 +379,8 @@ def to_graphics(recordtypes: list[db.Entity], filename: str,
                 print("Executing:", cmd)
 
             if os.system(cmd) != 0:  # TODO: replace with subprocess.run
-                raise Exception("An error occured during the execution of plantuml. "
+                raise Exception("An error occured during the execution of "
+                                "plantuml. "
                                 "Is plantuml installed?")
-            shutil.copy(os.path.join(td, filename + "." + extension), output_dirname)
+            shutil.copy(os.path.join(td, filename + "." + extension),
+                        output_dirname)