#vulnerable code 
                                @Override
    public boolean equals(Object obj) {
        if (obj instanceof Function) {
            Function fo = (Function) obj;
            return (fo.getFile().equals(getFile()) && fo.start == start);
        } else {
            return false;
        }
    } 
                            #location 5 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Override
    public boolean equals(Object obj) {
        if (obj instanceof Function) {
            Function fo = (Function) obj;
            return (fo.file.equals(file) && fo.start == start);
        } else {
            return false;
        }
    }