def _load_mtl_key(mtl, keys, band=None):
    """
    Loads requested metadata from a Landsat MTL dict

    Parameters
    -----------
    mtl: dict
        parsed Landsat 8 MTL metadata
    keys: iterable
        a list containing arbitrary keys to load from the MTL
    band: int
        band number to join to last key value
        (ignored if not int)

    Returns
    --------
    output: any value
        the value corresponding to the provided key in the MTL
    """
    keys = list(keys)
    if isinstance(band, int):
        keys[-1] = '%s%s' % (keys[-1], band)
    for k in keys:
        mtl = mtl[k]
    return mtl
