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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 extract_version():
 """Extract the version from the package."""

    with open('pdftools/__init__.py', 'r') as f:
        content = f.read()

    version_match = _version_re.search(content)
    version = str(ast.literal_eval(version_match.group(1)))
    return version