code: def parse_pair_args(labels, argclass):
    
    label_data = set()
    for arg in labels:
      name, value = split_pair(arg, '=', nullable_idx=1)
      label_data.add(argclass(name, value))
    return label_data
docs: Parse flags of key=value pairs and return a list of argclass.
  
    For pair variables, we need to:
       * split the input into name=value pairs (value optional)
       * Create the EnvParam object
  
    Args:
      labels: list of 'key' or 'key=value' strings.
      argclass: Container class for args, must instantiate with argclass(k, v).
  
    Returns:
      list of argclass objects.