Method tryCallPull

\brief Determine if the given subgraph variable can act as a parameter to the given CALL op We assume the variable flows as a parameter to the CALL. If the CALL doesn't lock the parameter size, create a PatchRecord within the subgraph that allows the CALL to take the parameter with its smaller logical size. \param op is the given CALL op \param rvn is the given subgraph variable acting as a param