Fix some Bugs of Undefined Variable

[Jiangxinz]

PR types

Bug fixes

PR changes

Others

Describe

1. python/paddle/tests/test_model.py:
   Line129: undefine variable name self,
   use 'cls' instead of 'self'.
2. python/paddle/fluid/tests/unittests/xpu/test_pool2d_op_xpu.py:
   Line 57, 59, 97, 99, 203, 211: undefine variable name adaptive_start_index,
   Line 58, 60, 98, 100, 204, 212: undefine variable name adaptive_end_index,
   from test_pool2d_op import adaptive_start_index, adaptive_end_index
3. python/paddle/fluid/optimizer.py:
   Line 1472: Undefined variable 'value',
   use 'num_trainers' instead of 'value'.
   Line 1926: Undefined variable 'warnings',
   import warnings
   Line 5687: Undefined variable 'fluid'
   import paddle.fluid as fluid
4. python/paddle/optimizer/optimizer.py
   Line 313: Undefined variable 'item'
   use 'model_np' instead of 'item'.
   Line 317: Undefined variable 'item'
   use 'model_np' instead of 'item'.
5. python/paddle/distributed/utils.py
   Line 387: Undefined variable 'distutils'
   from distutils.util import strtobool
6. python/paddle/fluid/tests/unittests/test_eager_deletion_delete_vars.py
   Line 178: Undefined variable 'persistables'
   use 'persistables' instead of 'persitables' in line 148
7. python/paddle/text/datasets/wmt14.py
   Line 194, 195: Undefined variable 'six'
   import six
8. python/paddle/fluid/tests/unittests/mkldnn/test_conv2d_transpose_mkldnn_op.py
   Line 158: Undefined variable 'enable_static'
   from paddle import enable_static
9. python/paddle/optimizer/lr.py
   Line 1352: Undefined variable 'loss'
   use 'metrics' instead of 'loss'
10. python/paddle/fluid/dataloader/collate.py
    Line 81: Undefined variable 'outputs'
    remove return outputs

[paddle-bot-old]

Thanks for your contribution!
Please wait for the result of CI firstly. See Paddle CI Manual for details.

[lelelelelez]

LGTM