show help on a parameter

def param_help(self, args):
        '''show help on a parameter'''
        if len(args) == 0:
            print("Usage: param help PARAMETER_NAME")
            return
        if self.vehicle_name is None:
            print("Unknown vehicle type")
            return
        path = mp_util.dot_mavproxy("%s.xml" % self.vehicle_name)
        if not os.path.exists(path):
            print("Please run 'param download' first (vehicle_name=%s)" % self.vehicle_name)
            return
        xml = open(path).read()
        from lxml import objectify
        objectify.enable_recursive_str()
        tree = objectify.fromstring(xml)
        htree = {}
        for p in tree.vehicles.parameters.param:
            n = p.get('name').split(':')[1]
            htree[n] = p
        for lib in tree.libraries.parameters:
            for p in lib.param:
                n = p.get('name')
                htree[n] = p
        for h in args:
            if h in htree:
                help = htree[h]
                print("%s: %s\n" % (h, help.get('humanName')))
                print(help.get('documentation'))
                try:
                    vchild = help.getchildren()[0]
                    print("\nValues: ")
                    for v in vchild.value:
                        print("\t%s : %s" % (v.get('code'), str(v)))
                except Exception as e:
                    pass
            else:
                print("Parameter '%s' not found in documentation" % h)