Clarify 'search_matches' docs.

Author: stefanseefeld

doc/design.txt

@@ -475,15 +475,15 @@ Here is the interface provided by the hyperdatabase::
             match the 'filter' spec, sorted by the group spec and then the
             sort spec.
 
+            "search_matches" is a container type
+
             "filterspec" is {propname: value(s)}
 
             "sort" and "group" are [(dir, prop), ...] where dir is '+', '-'
             or None and prop is a prop name or None. Note that for
             backward-compatibility reasons a single (dir, prop) tuple is
             also allowed.
 
-            "search_matches" is {nodeid: marker}
-
             The filter must match all properties specificed. If the property
             value to match is a list:
 

roundup/hyperdb.py

@@ -1129,7 +1129,7 @@ def filter(self, search_matches, filterspec, sort=[], group=[]):
         backward-compatibility reasons a single (dir, prop) tuple is
         also allowed.
 
-        "search_matches" is a sequence type
+        "search_matches" is a container type
 
         The filter must match all properties specificed. If the property
         value to match is a list: