code: def get(self, amendment_id, content=None, **kwargs):
          
          assert AMENDMENT_ID_PATTERN.match(amendment_id)
          r = self.get_amendment(amendment_id)
          if isinstance(r, dict) and ('data' in r):
              return r['data']
          return r
docs: Syntactic sugar around to make it easier to get fine-grained access
          to the parts of a file without composing a PhyloSchema object.
          Possible invocations include:
              w.get('pg_10')
              w.get('pg_10', 'trees')
              w.get('pg_10', 'trees', format='nexus')
              w.get('pg_10', tree_id='tree3')
          see: