add isUninitialized accessor for InputTag

Author: kpedro88

FWCore/Utilities/interface/InputTag.h

@@ -44,6 +44,8 @@ namespace edm {
 
     void cacheToken(EDGetToken) const;
 
+    bool isUninitialized() const;
+
     static const std::string kSkipCurrentProcess;
     static const std::string kCurrentProcess;
 

FWCore/Utilities/src/InputTag.cc

@@ -108,6 +108,10 @@ namespace edm {
 
   void InputTag::cacheToken(EDGetToken token) const { token_.store(token); }
 
+  bool InputTag::isUninitialized() const {
+    return label_.empty() and instance_.empty() and process_.empty();
+  }
+
   std::ostream& operator<<(std::ostream& ost, InputTag const& tag) {
     static std::string const process(", process = ");
     ost << "InputTag:  label = " << tag.label() << ", instance = " << tag.instance()