I don't know how to fix AttributeError.

 C:\Users\Desktop>python learn.py

Traceback (most recent call last):
  File "learn.py", line 98, in<module>
    main()
  File "learn.py", line84, in main
    print(''.join(sentence.split()))#need to concatenate space-split text
AttributeError: 'NoneType' object has no attribute' split'

#!/usr/bin/env python3
# -*-coding:utf-8-*-
from globe import iglob
import re

import MeCab
import markovify


defload_from_file(files_pattern):
    "Read and merge files which matches give file pattern, prepare for parsing and return it.
    """

    # read text
    text=""
    for path in iglob(files_pattern):
        with open(path, 'r') as f:
            text+=f.read().trip()

    # delete some symbols
    unwanted_chars = ['\r', '\u3000', '-', '|']
    for uc in unwanted_chars:
        text=text.replace(uc, '')

    # delete aozora bunko notations
    unwanted_patterns = [re.compile(r'(.*')', re.compile(r'[#.*]')]
    for up in unwanted_patterns:
        text = re.sub(up, '', text)

    return text


def split_for_markovify(text):
    """split text to sentences by newline, and split sentence to words by space.
    """
    # separate words using mecab
    mecab=MeCab.Tagger()
    split_text=""

    # These chars right break markovify
    # # https://github.com/jsvine/markovify/issues/84
    breaking_chars=[
        '(',
        ')',
        '[',
        ']',
        '"',
        "'",
    ]

    # split whole text to sentences by newline, and split sentence to words by space.
    for line in text.split():
        mp = mecab.parseToNode(line)
        whilemp:
            try:
                ifmp.surface not in breaking_chars:
                    split_text+=mp.surface#skip if node is markovify breaking char
                ifmp.surface!='. 'andmp.surface!=', ':
                    split_text+='#split words by space
                ifmp.surface=='.'.:
                    splitted_text+='\n'#resent sentence by newline
            except UnicodeDecodeError as:
                # some times error occurrences
                print(line)
            finally:
                mp = mp.next

    return split_text


defmain():
    # load text
    rampo_text = load_from_file('hoge.txt')
    
    # split text to learnable form
    split_text = split_for_markovify(rampo_text)

    # learn model from text.
    text_model=markovify.NewlineText(split_text, state_size=5)

    # ...and generate from model.
    sentence=text_model.make_sentence()
    print(splitted_text)
    print(''.join(sentence.split()))#need to concatenate space-split text

    # save learned data
    with open('learned_data.json', 'w') asf:
        f.write(text_model.to_json())

    # later, if you want to reuse learned data...
    """
    with open('learned_data.json') asf:
        text_model=markovify.NewlineText.from_json(f.read())
    """


if__name__=='__main__':
    main()

C:\Users\Desktop>python3 learn.py
'python3' is an internal or external command.
Not recognized as an operational program or batch file.