if this is the format you want…

```python
In [1]: from lib.iarc.utils import REVERSE_DESC_MAPPING, DESC_MAPPING

In [2]: REVERSE_DESC_MAPPING
Out[2]: 
{mkt.constants.ratingsbodies.CLASSIND: {'has_classind_criminal_acts': u'Atos Crim\xednosos',
  'has_classind_drugs': u'Drogas',
  'has_classind_drugs_illegal': u'Drogas Il\xedcitas',
  'has_classind_drugs_legal': u'Drogas L\xedcitas',
  'has_classind_lang': u'Linguagem Impr\xf3pria',
  'has_classind_no_descs': u'N\xe3o h\xe1 inadequa\xe7\xf5es',
  'has_classind_nudity': u'Nudez',
  'has_classind_sex_content': u'Sexo',
  'has_classind_sex_explicit': u'Sexo Expl\xedcito',
  'has_classind_shocking': u'Conte\xfado Impactante',
  'has_classind_violence': u'Viol\xeancia',
  'has_classind_violence_extreme': u'Viol\xeancia Extrema'},
 mkt.constants.ratingsbodies.GENERIC: {'has_generic_alcohol_ref': u'Alcohol Reference',
  'has_generic_blood': u'Blood',
  'has_generic_blood_gore': u'Blood and Gore',
  'has_generic_crude_humor': u'Crude Humor',
  'has_generic_drug_ref': u'Drug Reference',
  'has_generic_fantasy_violence': u'Fantasy Violence',
  'has_generic_intense_violence': u'Intense Violence',
  'has_generic_lang': u'Language',
  'has_generic_mild_blood': u'Mild Blood',
  'has_generic_mild_fantasy_violence': u'Mild Fantasy Violence',
  'has_generic_mild_lang': u'Mild Language',
  'has_generic_mild_violence': u'Mild Violence',
  'has_generic_nudity': u'Nudity',
  'has_generic_partial_nudity': u'Partial Nudity',
  'has_generic_real_gambling': u'Real Gambling',
  'has_generic_sex_content': u'Sexual Content',
  'has_generic_sex_themes': u'Sexual Themes',
  'has_generic_sim_gambling': u'Simulated Gambling',
  'has_generic_strong_lang': u'Strong Language',
  'has_generic_strong_sex_content': u'Strong Sexual Content',
  'has_generic_suggestive': u'Suggestive Themes'},
 mkt.constants.ratingsbodies.USK: {'has_usk_discrimination': u'Diskriminierung',
  'has_usk_drugs': u'Drogen',
  'has_usk_lang': u'Explizite Sprache',
  'has_usk_no_descs': u'No Descriptors',
  'has_usk_scary': u'\xc4ngstigende Inhalte',
  'has_usk_sex_content': u'Erotik/Sexuelle Inhalte',
  'has_usk_violence': u'Gewalt'},
 mkt.constants.ratingsbodies.ESRB: {'has_esrb_alcohol': u'Alcohol Reference',
  'has_esrb_alcohol_tobacco_ref': u'Alcohol and Tobacco Reference',
  'has_esrb_alcohol_tobacco_use': u'Use of Alcohol and Tobacco',
  'has_esrb_alcohol_use': u'Use of Alcohol',
  'has_esrb_blood': u'Blood',
  'has_esrb_blood_gore': u'Blood and Gore',
  'has_esrb_comic_mischief': u'Comic Mischief ',
  'has_esrb_crime': u'Crime',
  'has_esrb_crime_instruct': u'Criminal Instruction',
  'has_esrb_crude_humor': u'Crude Humor',
  'has_esrb_drug_alcohol_ref': u'Drug and Alcohol Reference',
  'has_esrb_drug_alcohol_tobacco_ref': u'Drug, Alcohol and Tobacco Reference',
  'has_esrb_drug_alcohol_tobacco_use': u'Use of Drug, Alcohol and Tobacco',
  'has_esrb_drug_alcohol_use': u'Use of Drug and Alcohol',
  'has_esrb_drug_ref': u'Drug Reference',
  'has_esrb_drug_tobacco_ref': u'Drug and Tobacco Reference',
  'has_esrb_drug_tobacco_use': u'Use of Drug and Tobacco',
  'has_esrb_drug_use': u'Use of Drugs',
  'has_esrb_fantasy_violence': u'Fantasy Violence',
  'has_esrb_hate_speech': u'Hate Speech',
  'has_esrb_intense_violence': u'Intense Violence',
  'has_esrb_lang': u'Language',
  'has_esrb_mild_blood': u'Mild Blood',
  'has_esrb_mild_fantasy_violence': u'Mild Fantasy Violence',
  'has_esrb_mild_lang': u'Mild Language',
  'has_esrb_mild_violence': u'Mild Violence',
  'has_esrb_no_descs': u'No Descriptors',
  'has_esrb_nudity': u'Nudity',
  'has_esrb_partial_nudity': u'Partial Nudity',
  'has_esrb_real_gambling': u'Real Gambling',
  'has_esrb_scary': u'Scary Themes',
  'has_esrb_sex_content': u'Sexual Content',
  'has_esrb_sex_themes': u'Sexual Themes',
  'has_esrb_sim_gambling': u'Simulated Gambling',
  'has_esrb_strong_lang': u'Strong Language',
  'has_esrb_strong_sex_content': u'Strong Sexual Content',
  'has_esrb_suggestive': u'Suggestive Themes',
  'has_esrb_tobacco_ref': u'Tobacco Reference',
  'has_esrb_tobacco_use': u'Use of Tobacco',
  'has_esrb_violence': u'Violence',
  'has_esrb_violence_ref': u'Violent References'},
 mkt.constants.ratingsbodies.PEGI: {'has_pegi_discrimination': u'Discrimination',
  'has_pegi_drugs': u'Drugs',
  'has_pegi_gambling': u'Gambling',
  'has_pegi_lang': u'Language',
  'has_pegi_no_descs': u'No Descriptors',
  'has_pegi_online': u'Online',
  'has_pegi_scary': u'Fear',
  'has_pegi_sex_content': u'Sex',
  'has_pegi_violence': u'Violence'}}
```

I would recommend this change:

```diff
diff --git a/lib/iarc/utils.py b/lib/iarc/utils.py
index c8e6c43..f3d5f37 100644
--- a/lib/iarc/utils.py
+++ b/lib/iarc/utils.py
@@ -299,15 +299,17 @@ DESC_MAPPING = {
 }
 
 
+REVERSE_DESC_MAPPING = {}
+
 for body, mappings in DESC_MAPPING.items():
     for native_desc, desc_slug in mappings.items():
-        DESC_MAPPING[body][native_desc] = 'has_{0}_{1}'.format(
-            body.iarc_name, desc_slug).lower()
+        val = 'has_{0}_{1}'.format(body.iarc_name, desc_slug).lower()
+
+        # {body: {'key': 'val'}}
+        DESC_MAPPING[body][native_desc] = val
 
-# Change {body: {'key': 'val'}} to {body: {'val': 'key'}}.
-REVERSE_DESC_MAPPING = reduce(lambda a, b: dict(a, **b),
-    [dict((unicode(v), unicode(k)) for k, v in body_mapping.iteritems())
-     for body, body_mapping in DESC_MAPPING.iteritems()])
+        # {body: {'val': 'val'}}
+        REVERSE_DESC_MAPPING.setdefault(body, {})[val] = native_desc
 
 
 INTERACTIVES_MAPPING = {
```