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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( 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. 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(
        src_fs, "/", dst_fs, "/", walker=walker, on_copy=on_copy, workers=workers
    )