How to set initial state in Python

I want to set intial state input x0 for every iteration.
If the function ocp.constraints.x0(Python Interface — acados documentation) can meet my needs.
And I observe that some scholar set inital state input by

AcadosOcpSolver.set(0, 'lbx', x_current)
AcadosOcpSolver.set(0, 'ubx', x_current)

which can set intial state input.
But why it can


the first function is to set the initial state when formulating the ocp, i.e. interacting with AcadosOcp object.
The latter can be used to interact with the ocp solver, i.e. the AcadosOcpSolver object.