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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def copy_fs_if_newer( src_fs, # type: Union[FS, Text] dst_fs, # type: Union[FS, Text] walker=None, # type: Optional[Walker] on_copy=None, # type: Optional[_OnCopy] workers=0, # type: int ):
 """Copy the contents of one filesystem to another, checking times. If both source and destination files exist, the copy is executed only if the source file is newer than the destination file. In case modification times of source or destination files are not available, copy file is always executed. Arguments: src_fs (FS or str):
 Source filesystem (URL or instance). dst_fs (FS or str):
 Destination filesystem (URL or instance). walker (~fs.walk.Walker, optional):
 A walker object that will be used to scan for files in ``src_fs``. Set this if you only want to consider a sub-set of the resources in ``src_fs``. on_copy (callable):
A function callback called after a single file copy is executed. Expected signature is ``(src_fs, src_path, dst_fs, dst_path)``. workers (int):
 Use ``worker`` threads to copy data, or ``0`` (default) for a single-threaded copy. """

    return copy_dir_if_newer(
        src_fs, "/", dst_fs, "/", walker=walker, on_copy=on_copy, workers=workers
    )