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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 tokenize(text):
 """ Yield tokens. Args: text (str):
 The original text. Yields: dict: The next token. """


    stem = PorterStemmer().stem
    tokens = re.finditer('[a-z]+', text.lower())

    for offset, match in enumerate(tokens):

        # Get the raw token.
        unstemmed = match.group(0)

        yield { # Emit the token.
            'stemmed':      stem(unstemmed),
            'unstemmed':    unstemmed,
            'offset':       offset
        }