code: @Nonnull
      public BugInstance addCalledMethod(MethodGen methodGen, InvokeInstruction inv) {
          ConstantPoolGen cpg = methodGen.getConstantPool();
          return addCalledMethod(cpg, inv);
      }
docs: Add a method annotation for the method which is called by given
  instruction.
  
  @param methodGen
  the method containing the call
  @param inv
  the InvokeInstruction
  @return this object