docs: def store_sample_set(self, md5_list):
          """ Store a sample set (which is just a list of md5s).
  
              Note: All md5s must already be in the data store.
  
              Args:
                  md5_list: a list of the md5s in this set (all must exist in data store)
  
              Returns:
                  The md5 of the set (the actual md5 of the set)
          """
  
          # Sanity check
          if not md5_list:
              print 'Warning: Trying to store an empty sample_set'
              return None
  
          # Remove any duplicates
          md5_list = list(set(md5_list))
  
          for md5 in md5_list:
              if not self.has_sample(md5):
                  raise RuntimeError('%s: Not found! All items in sample_set must be in the datastore' % (md5))
          set_md5 = hashlib.md5(str(md5_list)).hexdigest()
          self._store_work_results({'md5_list':md5_list}, 'sample_set', set_md5)
          return set_md5