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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 replace_variables(sentence: List[str], sentence_variables: Dict[str, str]) -> Tuple[List[str], List[str]]: """ Replaces abstract variables in text with their concrete counterparts. """

    tokens = []
    tags = []
    for token in sentence:
        if token not in sentence_variables:
            tokens.append(token)
            tags.append("O")
        else:
            for word in sentence_variables[token].split():
                tokens.append(word)
                tags.append(token)
    return tokens, tags