xep_0030: add docstring to get_info_from_domain

Signed-off-by: Maxime “pep” Buquet <pep@bouah.net>

slixmpp/plugins/xep_0030/disco.py

@@ -300,6 +300,8 @@ class XEP_0030(BasePlugin):
 
     async def get_info_from_domain(self, domain=None, timeout=None,
                                    cached=True, callback=None):
+        """Fetch disco#info of specified domain and one disco#items level below"""
+
         if domain is None:
             domain = self.xmpp.boundjid.domain