diff --git a/src/wireviz/Harness.py b/src/wireviz/Harness.py
index 29d0e0b..1c62052 100644
--- a/src/wireviz/Harness.py
+++ b/src/wireviz/Harness.py
@@ -328,6 +328,26 @@ class Harness:
 
         return bytes(string, encoding='utf-8')
 
+    @property
+    def csv(self):
+        raise NotImplementedError
+
+    @property
+    def csv_excel(self):
+        raise NotImplementedError
+
+    @property
+    def csv_unix(self):
+        raise NotImplementedError
+
+    @property
+    def tsv(self):
+        raise NotImplementedError
+
+    @property
+    def tsv_excel(self):
+        raise NotImplementedError
+
     def output(self, filename: (str, Path), view: bool = False, cleanup: bool = True, fmt: tuple = ('pdf', )) -> None:
         # graphical output
         graph = self.create_graph()
diff --git a/src/wireviz/wireviz.py b/src/wireviz/wireviz.py
index e6aed08..6d3fcec 100755
--- a/src/wireviz/wireviz.py
+++ b/src/wireviz/wireviz.py
@@ -179,12 +179,24 @@ def parse(yaml_input: str, file_out: (str, Path) = None, return_types: (None, st
         for rt in return_types:
             if rt == 'png':
                 returns.append(harness.png)
-            if rt == 'svg':
+            elif rt == 'svg':
                 returns.append(harness.svg)
-            if rt == 'html':
+            elif rt == 'html':
                 returns.append(harness.html)
-            if rt == 'harness':
+            elif rt == 'csv':
+                returns.append(harness.csv)
+            elif rt == 'csv_excel':
+                returns.append(harness.csv_excel)
+            elif rt == 'csv_unix':
+                returns.append(harness.csv_unix)
+            elif rt == 'tsv':
+                returns.append(harness.tsv)
+            elif rt == 'tsv_excel':
+                returns.append(harness.tsv_excel)
+            elif rt == 'harness':
                 returns.append(harness)
+            else:
+                raise ValueError(f'return type "{rt}" not supported')
 
         return tuple(returns) if len(returns) != 1 else returns[0]
 
@@ -208,7 +220,9 @@ def parse_file(yaml_file: str, file_out: (str, Path) = None) -> None:
 def main(input_file, prepend, out):
     """
     Take a YAML file containing a harness specification and, utilizing GraphViz,
-    translate that specification into various output formats.  Example:
+    translate that specification into various output formats.
+
+    Example:
 
         $>wireviz my_input_file.yml -o png -o svg
     """