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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 from_git_rev_read(path):
 """Retrieve given file path contents of certain Git revision."""

    if ":" not in path:
        raise ValueError("Path identifier must start with a revision hash.")

    cmd = "git", "show", "-t", path
    try:
        return subprocess.check_output(cmd).rstrip().decode("utf-8")
    except subprocess.CalledProcessError:
        raise ValueError