Convert a document into a list of tokens.

    This lowercases, tokenizes, de-accents (optional). -- the output are final
    tokens = unicode strings, that won't be processed any further.

def simple_preprocess(doc, deacc=False, min_len=2, max_len=15):
    """
    Convert a document into a list of tokens.

    This lowercases, tokenizes, de-accents (optional). -- the output are final
    tokens = unicode strings, that won't be processed any further.

    """
    tokens = [
        token for token in tokenize(doc, lower=True, deacc=deacc, errors='ignore')
        if min_len <= len(token) <= max_len and not token.startswith('_')
    ]
    return tokens