Construct a dependency graph based on given parameters.

        :param targets:             A list of tuples like (CFGNode, statement ID)
        :param control_flow_slice:  Is the backward slicing only depends on CFG or not.

def _construct(self, targets, control_flow_slice=False):
        """
        Construct a dependency graph based on given parameters.

        :param targets:             A list of tuples like (CFGNode, statement ID)
        :param control_flow_slice:  Is the backward slicing only depends on CFG or not.
        """

        if control_flow_slice:
            simruns = [ r for r, _ in targets ]
            self._construct_control_flow_slice(simruns)

        else:
            self._construct_default(targets)