code: def _lookup_key_parse(table_keys):
      
      # we need to parse the key lookup passed in
      regex_matcher = '\[([^\]]+)]'
      valid_dynamodb_datatypes = ['M', 'S', 'N', 'L']
      clean_table_keys = []
      new_keys = []
  
      for key in table_keys:
          match = re.search(regex_matcher, key)
          if match:
              # the datatypes are pulled from the dynamodb docs
              if match.group(1) in valid_dynamodb_datatypes:
                  match_val = str(match.group(1))
                  key = key.replace(match.group(0), '')
                  new_keys.append({match_val: key})
                  clean_table_keys.append(key)
              else:
                  raise ValueError(
                      ('Stacker does not support looking up the datatype: {}')
                      .format(str(match.group(1))))
          else:
              new_keys.append({'S': key})
              clean_table_keys.append(key)
      key_dict = {}
      key_dict['new_keys'] = new_keys
      key_dict['clean_table_keys'] = clean_table_keys
  
      return key_dict
docs: Return the order in which the stacks should be executed.
  
      Args:
          dependencies (dict): a dictionary where each key should be the
              fully qualified name of a stack whose value is an array of
              fully qualified stack names that the stack depends on. This is
              used to generate the order in which the stacks should be
              executed.
  
      Returns:
          dict: includes a dict of lookup types with data types ('new_keys')
                and a list of the lookups with without ('clean_table_keys')