def flatten_voting_method(method):
    """Flatten a voting method data structure.

    The incoming ``method`` data structure is as follows. At the time of
    writing, all elections have an identical structure. In practice. the None
    values could be different scalars. ::

      {
        "instructions": {
          "voting-id": {
            "en_US": None,
          },
        },
        "excuse-required":  None,
        "start": None,
        "end": None,
        "primary": None,
        "type": None,
      }

    This function flattens the US English voting ID instructions to become a top
    level item like all of the others.

    Args:
        method (dict): A nested voting method data structure.

    Returns:
        dict: A flat voting method data structure.
    """
    flat_method = {k: v for k, v in method.items() if k != "instructions"}
    flat_method["instructions"] = method["instructions"]["voting-id"]["en_US"]
    return flat_method