doc: SCHWED-6108 improved comments on chain_type

modules/mol/base/src/chain_type.cc

@@ -78,6 +78,8 @@ String StringFromChainType(ChainType type)
 {
   // chain types as found in the entity category of a mmcif file
   if (CHAINTYPE_POLY == type) {
+    // "polymer" in _entity.type
+    // "other" in _entity_poly.type
     return "polymer";
   } else if (CHAINTYPE_NON_POLY == type) {
     return "non-polymer";

modules/mol/base/src/chain_type.hh

@@ -30,8 +30,8 @@ namespace ost { namespace mol {
 /// \enum different kinds of chains
 ///
 /// Warning: this class mixes vocabulary from _entity.type and
-// _entity_poly.type, which is more detailed. As a result it cannot be used to
-/// to read/write mmCIF entity types accurately.
+// _entity_poly.type, which is more detailed. As a result it is not a 1:1
+// mapping and cannot be used to to read/write mmCIF entity types accurately.
 
 typedef enum {
   CHAINTYPE_POLY,           ///< polymer