docs: def get_flattened(dct, names, path_joiner="_"):
    """Flatten a child dicts, whose resulting keys are joined by path_joiner.
  
    E.G. { "valuation": { "currency": "USD", "amount": "100" } } ->
         { "valuation_currency": "USD", "valuation_amount": "100" }
    """
    new_dct = dict()
    for key, val in dct.items():
      if key in names:
        child = {path_joiner.join(k): v for k, v in flatten_dict(val, (key, ))}
        new_dct.update(child)
      else:
        new_dct[key] = dct[key]
    return new_dct