Add a doc example for simplifiable-if-expression and simplifiable-if-statement

Refs #5953
Closes #5882

Author: Pierre-Sassoulas

doc/data/messages/s/simplifiable-if-expression/bad.py

@@ -0,0 +1,5 @@
+FLYING_THINGS = ["bird", "plane", "superman", "this example"]
+
+
+def is_flying_thing(an_object):
+    return True if an_object in FLYING_THINGS else False  # [simplifiable-if-expression]

doc/data/messages/s/simplifiable-if-expression/details.rst

@@ -1 +1,5 @@
-# This is a placeholder for correct code for this message.
+FLYING_THINGS = ["bird", "plane", "superman", "this example"]
+
+
+def is_flying_thing(an_object):
+    return an_object in FLYING_THINGS

doc/data/messages/s/simplifiable-if-expression/good.py

@@ -0,0 +1 @@
+- `Simplifying an 'if' statement with bool() <https://stackoverflow.com/questions/49546992/>`_

doc/data/messages/s/simplifiable-if-expression/related.rst

@@ -0,0 +1,9 @@
+FLYING_THINGS = ["bird", "plane", "superman", "this example"]
+
+
+def is_flying_animal(an_object):
+    if isinstance(an_object, Animal) and an_object in FLYING_THINGS:  # [simplifiable-if-statement]
+        is_flying = True
+    else:
+        is_flying = False
+    return is_flying

doc/data/messages/s/simplifiable-if-statement/bad.py

@@ -1 +1,6 @@
-# This is a placeholder for correct code for this message.
+FLYING_THINGS = ["bird", "plane", "superman", "this example"]
+
+
+def is_flying_animal(an_object):
+    is_flying = isinstance(an_object, Animal) and an_object.name in FLYING_THINGS
+    return is_flying

doc/data/messages/s/simplifiable-if-statement/details.rst

@@ -7,21 +7,46 @@ def test_simplifiable_1(arg):
     # Simple test that can be replaced by bool(arg)
     return True if arg else False # [simplifiable-if-expression]
 
+
 def test_simplifiable_2(arg):
     # Simple test that can be replaced by not arg
     return False if arg else True # [simplifiable-if-expression]
 
+
 def test_simplifiable_3(arg):
     # Simple test that can be replaced by arg == 1
     return True if arg == 1 else False # [simplifiable-if-expression]
 
+
 def test_simplifiable_4(arg):
     # Simple test that can be replaced by not (arg == 1)
     return False if arg == 1 else True # [simplifiable-if-expression]
 
+
 def test_not_simplifiable(arg):
     x = True if arg else True
     y = 0 if arg else 1
     t = False if arg != 1 else False
     t2 = None if arg > 3 else False
     return x, y, t, t2
+
+
+def x():
+    a = []
+    b = []
+    if bool('special test'):
+        a = True
+    else:
+        b = False
+    return a + b
+
+FLYING_THINGS = ["bird", "plane", "superman", "this example"]
+
+
+def is_flying_animal(an_object):
+    is_flying = False
+    if isinstance(an_object, str) and an_object in FLYING_THINGS:  # [simplifiable-if-statement]
+        is_flying = True
+    else:
+        is_flying = False
+    return is_flying