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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 within_proj_dir(path='.'):
 # type: (Optional[str]) -> str """ Return an absolute path to the given project relative path. :param path: Project relative path that will be converted to the system wide absolute path. :return: Absolute path. """

    curr_dir = os.getcwd()

    os.chdir(proj_path(path))

    yield

    os.chdir(curr_dir)