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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 is_valid_bibtex(reference):
 """ Use pybtex to validate that a reference is in proper BibTeX format Args: reference: A String reference in BibTeX format. Returns: Boolean indicating if reference is valid bibtex. """

    # str is necessary since pybtex seems to have an issue with unicode. The
    # filter expression removes all non-ASCII characters.
    sio = StringIO(remove_non_ascii(reference))
    parser = bibtex.Parser()
    errors.set_strict_mode(False)
    bib_data = parser.parse_stream(sio)
    return len(bib_data.entries) > 0