In creole template support of %%lead.follower2 and %%lead['follower2'] notation

%if 'follower1' in %%lead now search if a follower exists has follower

src/rougail/template/base.py

@@ -74,12 +74,21 @@ class RougailLeaderIndex:
 
     def __getattr__(self, name):
         if name not in self._follower:
-            raise AttributeError()
+            raise AttributeError(f'unable to find follower "{name}"')
         value = self._follower[name]
         if isinstance(value, PropertiesOptionError):
-            raise AttributeError()
+            raise AttributeError(f'unable to access to follower "{name}": {value}')
         return value
 
+    def __getitem__(self, name):
+        return self.__getattr__(name)
+
+    def __contains__(self, name):
+        if self._follower.__contains__(name):
+            value = self._follower[name]
+            return not isinstance(value, PropertiesOptionError)
+        return False
+
     def __str__(self):
         return str(self._value)
 
@@ -141,7 +150,7 @@ class RougailLeader:
     def __contains__(self, value):
         return self._value.__contains__(value)
 
-    async def add_follower(self,
+    async def _add_follower(self,
                             config,
                             name: str,
                             path: str,
@@ -389,7 +398,7 @@ class RougailBaseTemplate:
                             if is_variable_namespace:
                                 self.rougail_variables_dict[await suboption.option.name()] = leader
                         else:
-                            await leader.add_follower(self.config,
+                            await leader._add_follower(self.config,
                                                        await suboption.option.name(),
                                                        await suboption.option.path(),
                                                        )

tests/dictionaries/40ifin_leadershipauto/result/etc/mailname

@@ -1,2 +1,6 @@
+#attr
+leader: a
+follower2: 
+#key
 leader: a
 follower2: 

tests/dictionaries/40ifin_leadershipauto/tmpl/mailname

@@ -1,3 +1,4 @@
+#attr
 %for %%lead in %%leader
 leader: %%lead
 %if %%hasattr(%%lead, 'follower1')
@@ -7,3 +8,13 @@ follower1: %%lead.follower1
 follower2: %%lead.follower2
 %end if
 %end for
+#key
+%for %%lead in %%leader
+leader: %%lead
+%if 'follower1' in %%lead
+follower1: %%lead['follower1']
+%end if
+%if 'follower2' in %%lead
+follower2: %%lead['follower2']
+%end if
+%end for