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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 log(client, revision, format, no_output, paths):
 """Show logs for a file."""

    graph = Graph(client)
    if not paths:
        start, is_range, stop = revision.partition('..')
        if not is_range:
            stop = start
        elif not stop:
            stop = 'HEAD'

        commit = client.repo.rev_parse(stop)
        paths = (
            str(client.path / item.a_path)
            for item in commit.diff(commit.parents or NULL_TREE)
            # if not item.deleted_file
        )

    # NOTE shall we warn when "not no_output and not paths"?
    graph.build(paths=paths, revision=revision, can_be_cwl=no_output)

    FORMATS[format](graph)