#   Copyright 2020 AUI, Inc. Washington DC, USA
#
#   Licensed under the Apache License, Version 2.0 (the "License");
#   you may not use this file except in compliance with the License.
#   You may obtain a copy of the License at
#
#       http://www.apache.org/licenses/LICENSE-2.0
#
#   Unless required by applicable law or agreed to in writing, software
#   distributed under the License is distributed on an "AS IS" BASIS,
#   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#   See the License for the specific language governing permissions and
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def extend(vis_dataset,extend_parms,storage_parms):
    """
    .. todo::
        This function is not yet implemented
    
    Extend and grow existing flags.
    
    Options : grow-around, extendflags, growtime, growfreq, antint.. etc....
    
    Inputs :
    
    (1) algo parameters
    (2) array name for output flags. Default = FLAG
    (3) array name for input flags. Default = FLAG
        
    If a new flag_array is picked for the output, save only 'new' flags.
    They can be merged with pre-existing flags in a separate step
    
    If an existing flag_array is picked for the output, merge with logical OR.
    
    Returns
    -------
    vis_dataset : xarray.core.dataset.Dataset
    """

