Resolve "Robust remove() API"

implementing #239 (closed)

include/core/capture/capture_base.h

@@ -65,7 +65,7 @@ class CaptureBase : public NodeBase, public std::enable_shared_from_this<Capture
 
     public:
         virtual void setProblem(ProblemPtr _problem) final;
-        FeatureBasePtrList& getFeatureList();
+        const FeatureBasePtrList& getFeatureList() const;
 
         void getFactorList(FactorBasePtrList& _fac_list);
 
@@ -191,7 +191,7 @@ inline void CaptureBase::setFrame(const FrameBasePtr _frm_ptr)
     frame_ptr_ = _frm_ptr;
 }
 
-inline FeatureBasePtrList& CaptureBase::getFeatureList()
+inline const FeatureBasePtrList& CaptureBase::getFeatureList() const
 {
     return feature_list_;
 }