<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_void_volume_surfarea(structure, rad_dict=None, chan_rad=0.3, probe_rad=0.1):
 """ Computes the volume and surface area of isolated void using Zeo++. Useful to compute the volume and surface area of vacant site. Args: structure: pymatgen Structure containing vacancy rad_dict(optional):
 Dictionary with short name of elements and their radii. chan_rad(optional):
 Minimum channel Radius. probe_rad(optional):
 Probe radius for Monte Carlo sampling. Returns: volume: floating number representing the volume of void """

    with ScratchDir('.'):
        name = "temp_zeo"
        zeo_inp_filename = name + ".cssr"
        ZeoCssr(structure).write_file(zeo_inp_filename)

        rad_file = None
        if rad_dict:
            rad_file = name + ".rad"
            with open(rad_file, 'w') as fp:
                for el in rad_dict.keys():
                    fp.write("{0}     {1}".format(el, rad_dict[el]))

        atmnet = AtomNetwork.read_from_CSSR(zeo_inp_filename, True, rad_file)
        vol_str = volume(atmnet, 0.3, probe_rad, 10000)
        sa_str = surface_area(atmnet, 0.3, probe_rad, 10000)
        vol = None
        sa = None
        for line in vol_str.split("\n"):
            if "Number_of_pockets" in line:
                fields = line.split()
                if float(fields[1]) > 1:
                    vol = -1.0
                    break
                if float(fields[1]) == 0:
                    vol = -1.0
                    break
                vol = float(fields[3])
        for line in sa_str.split("\n"):
            if "Number_of_pockets" in line:
                fields = line.split()
                if float(fields[1]) > 1:
                    # raise ValueError("Too many voids")
                    sa = -1.0
                    break
                if float(fields[1]) == 0:
                    sa = -1.0
                    break
                sa = float(fields[3])

    if not vol or not sa:
        raise ValueError("Error in zeo++ output stream")
    return vol, sa