Splits text_string into a list of sentences based on NLTK's english.pickle tokenizer, and
    returns said list as type list of str.

    Keyword argument:

    - text_string: string instance

    Exceptions raised:

    - InputError: occurs should a non-string argument be passed

def create_sentence_list(text_string):
    '''
    Splits text_string into a list of sentences based on NLTK's english.pickle tokenizer, and
    returns said list as type list of str.

    Keyword argument:

    - text_string: string instance

    Exceptions raised:

    - InputError: occurs should a non-string argument be passed
    '''
    if text_string is None or text_string == "":
        return []
    elif isinstance(text_string, str):
        return SENTENCE_TOKENIZER.tokenize(text_string)
    else:
        raise InputError("non-string passed as argument for create_sentence_list")