Key('flow',
       Float(name='Flow_meter', units='Hz',
             help='Flow meter reading',
             FITS=('W_MCFLOW', 'MCP__COOLANT_FLOW'))),

def gatherHeaderCards(cmd, actor, modelNames=None, shortNames=False):
    """ Fetch and return all FITS cards defined in the given models.

    Args
    ----
    cmd : an actorcore Command
    actor : an actorcore Actor,
      Which contans .models.
    modelNames : None, or list of strings
      The actors to generate keys for. If None, all the models in actor.models
    shortNames : bool
      If True, use the short FITS names.

    Returns
    -------
    cards : list of fitsio-compatible card dictionaries.
      Suitable to get a header with "fitsio.FITSHDR(cards)"
    """

def startFitsFile(cmd, filename, cards,
                  img=None, clobber=False, doShortnameHDU=True):
    """ Write the PHDU and first HDU(s).

    Args
    ----
    cmd : an actorcore Command
    filename : string
       Full pathname for the FITS file.
    cards : list of fits cards
       fitsio compatible: strings or dictionaries
    img : None, or a 2-d image
    clobber : bool
       Whether to overwrite any existing file. In production, this should not happen.
    doShortnameHDU : bool
       Whether to create a translation HDU if we have short card names.

    """