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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 phrase(min_size, max_size = None):
 """ Generates a random phrase which consists of few words separated by spaces. The first word is capitalized, others are not. :param min_size: (optional) minimum string length. :param max_size: maximum string length. :return: a random phrase. """

        max_size = max_size if max_size != None else min_size
        size = RandomInteger.next_integer(min_size, max_size)
        if size <= 0:
            return ""
        
        result = ""
        result += random.choice(_all_words)
        while len(result) < size:
            result += " " + random.choice(_all_words).lower()

        return result