Author: Tim Booth <tbooth@ceh.ac.uk>
Last-Update: Fri, 28 Feb 2014 16:25:41 +0000
Description: Deal with cases when h_key xor h_value is set

--- a/biom/table.py
+++ b/biom/table.py
@@ -338,12 +338,8 @@ class Table(object):
 
         samp_ids = delim.join(map(str, self.SampleIds))
 
-        # 17 hrs of straight programming later...
-        if header_key is not None:
-            if header_value is None:
-                raise TableException, "You need to specify both header_key and header_value"
-        if header_value is not None:
-            if header_key is None:
+        # If h_key xor h_value is set we have a problem...
+        if (header_key is None) != (header_value is None):
                 raise TableException, "You need to specify both header_key and header_value"
 
         if header_value: