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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 get_git_root(index=3):
 # type: (int) -> str """ Get the path of the git root directory of the caller's file Raises a RuntimeError if a git repository cannot be found """

    path = get_current_path(index=index)
    while True:
        git_path = os.path.join(path, '.git')
        if os.path.isdir(git_path):
            return path
        if os.path.dirname(path) == path:
            raise RuntimeError("Cannot find git root")
        path = os.path.split(path)[0]