Method reassign_context

ThirdParty/libproj/vtklibproj/src/grids.cpp:1677–1680

                             const std::string &filename);

    void reassign_context(PJ_CONTEXT *ctx) override {
        m_ctx = ctx;
        m_fp->reassign_context(ctx);
    }

    bool hasChanged() const override { return m_fp->hasChanged(); }
};