Avoid loading the base interface each time a client is created

AFAIK, Interface is never modified after creation, so sharing the
base interface between clients should be completely fine (and save
some io and parsing).

Author: Rémy Noel

varlink/client.py

@@ -1,3 +1,4 @@
+import functools
 import importlib.resources
 import json
 import os
@@ -328,6 +329,13 @@ class Client:
 
     handler = SimpleClientInterfaceHandler
 
+    @classmethod
+    @functools.lru_cache(maxsize=1)
+    def _get_base_interface(cls):
+        return Interface(
+            importlib.resources.read_text("varlink", "org.varlink.service.varlink")
+        )
+
     def __init__(self, address=None, resolve_interface=None, resolver=None):
         """Creates a Client object to reach the interfaces of a varlink service.
         For more constructors see the class constructor methods new_with_*() returning an Client object.
@@ -345,10 +353,7 @@ def __init__(self, address=None, resolve_interface=None, resolver=None):
         self._child_pid = 0
         self._str = "Client<uninitialized>"
 
-        interface = Interface(
-            importlib.resources.read_text("varlink", "org.varlink.service.varlink")
-        )
-        self.add_interface(interface)
+        self.add_interface(self._get_base_interface())
 
         if resolve_interface:
             self._with_interface(resolve_interface, resolver)