How to use the rosdep.core.Rosdep function in rosdep

(verified_packages, rejected_packages) = roslib.stacks.expand_to_packages(rdargs)
        valid_stacks = [s for s in roslib.stacks.list_stacks() if s in rdargs]
    
        if len(rejected_packages) > 0:
            print("Warning: could not identify %s as a package"%rejected_packages)
        if len(verified_packages) == 0 and len(valid_stacks) == 0:
            parser.error("No Valid Packages or stacks listed as arguments")
                
    else: # rosdep as argumets 
        if options.rosdep_all:
            parser.error("-a, --all is not a valid option for this command")

    ### Find all dependencies
    try:
        r = core.Rosdep(verified_packages, robust=options.robust)
    except roslib.os_detect.OSDetectException as ex:
        print("rosdep ABORTING.  Failed to detect OS: %s"%ex)
        return 1

    except roslib.exceptions.ROSLibException as ex:
        print("rosdep ABORTING: %s"%ex)
        return 1

    if options.verbose:
        print("Detected OS: " + r.osi.get_name())
        print("Detected Version: " + r.osi.get_version())

    try:
        if command == "generate_bash" or command == "satisfy":
            missing_packages = r.satisfy()
            if not missing_packages: