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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 commentless(data):
 """ Generator that removes from a list of strings the double dot reStructuredText comments and its contents based on indentation, removing trailing empty lines after each comment as well. """

    it = iter(data)
    while True:
        line = next(it)
        while ":" in line or not line.lstrip().startswith(".."):
            yield line
            line = next(it)
        indent = indent_size(line)
        it = itertools.dropwhile(lambda el: indent_size(el) > indent
                                            or not el.strip(), it)