Pragmas in python

I'm reading bottle.py source code. It's a web framework, with only 3000+ lines python code. So cool.

I found some code like this:

class ServerAdapter(object):
    quiet = False
    def __init__(self, host='127.0.0.1', port=8080, **config):
        self.options = config
        self.host = host
        self.port = int(port)

    def run(self, handler): # pragma: no cover
        pass
    ... 

What does the # pragma: no cover mean? I can't find any introduce about the pragma syntax in the python documentations.