def valid_word(token):
    """
    Returns False if the spacy token is either
    - a punctuation, whitespace, number
    - a pronoun (indicated by the '-PRON-' flag), e.g. 'it'
    - the token is shorter than 2
    these words will be removed from the corpus
    """
    pron_flag = token.lemma_ != '-PRON-'
    word_flag = not (token.is_punct or token.is_space or token.like_num)
    word_len_flag = len(token) >= 2
    valid = pron_flag and word_flag and word_len_flag
    return valid