title: How to fix ' module 'keras.backend.tensorflow_backend' has no attribute '_is_tf_1''
body: <p>While training the yolov3 framework, there's always this module error</p>
  
  <p>I have tried reinstalling keras and tensorflow, and the version of keras is 2.3.0 and the version of tensorflow is 1.14.0.</p>
  
  <pre><code>Traceback (most recent call last):
    File "train.py", line 6, in &lt;module&gt;
      import keras.backend as K
    File "F:\Anacoda\lib\site-packages\keras\__init__.py", line 3, in &lt;module&gt;
      from . import utils
    File "F:\Anacoda\lib\site-packages\keras\utils\__init__.py", line 27, in &lt;module&gt;
      from .multi_gpu_utils import multi_gpu_model
    File "F:\Anacoda\lib\site-packages\keras\utils\multi_gpu_utils.py", line 7, in &lt;module&gt;
      from ..layers.merge import concatenate
    File "F:\Anacoda\lib\site-packages\keras\layers\__init__.py", line 4, in &lt;module&gt;
      from ..engine.base_layer import Layer
    File "F:\Anacoda\lib\site-packages\keras\engine\__init__.py", line 8, in &lt;module&gt;
      from .training import Model
    File "F:\Anacoda\lib\site-packages\keras\engine\training.py", line 21, in &lt;module&gt;
      from . import training_arrays
    File "F:\Anacoda\lib\site-packages\keras\engine\training_arrays.py", line 14, in &lt;module&gt;
      from .. import callbacks as cbks
    File "F:\Anacoda\lib\site-packages\keras\callbacks\__init__.py", line 19, in &lt;module&gt;
      if K.backend() == 'tensorflow' and not K.tensorflow_backend._is_tf_1():
  AttributeError: module 'keras.backend.tensorflow_backend' has no attribute '_is_tf_1'
  </code></pre>