<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def run_command(command, args):
 """ Run all tasks registered in a command. """

    for category, commands in iteritems(command_categories):
        for existing_command in commands:
            if existing_command.match(command):
                existing_command.run(args)