def clean_tokens(tokens):
    """Returns a list of lemmas from a list of spaCy tokens
    
    Args:
        tokens (list(spaCy_token)): the list of spaCy tokens to pull lemmas from
    
    Returns:
        list: a list of lemmas corresponding to the tokens passed in
    """
    cleaned_tokens = []
    for token in tokens:
        if not token.is_punct:
            if token.lemma_ == "-PRON-":
                cleaned_tokens.append(token.text)
            else:
                cleaned_tokens.append(token.lemma_)
    return cleaned_tokens