Changed relative imports to absolute to allow convert_graph_to_onnx.py to run as a script. (#14325)

* Changed relative imports to absolute to allow convert_graph_to_onnx.py to be run as a script

* isorted code

src/transformers/onnx/convert.py

@@ -20,10 +20,10 @@ from typing import Iterable, List, Tuple, Union
 import numpy as np
 from packaging.version import Version, parse
 
-from .. import PreTrainedModel, PreTrainedTokenizer, TensorType, TFPreTrainedModel, is_torch_available
-from ..file_utils import is_torch_onnx_dict_inputs_support_available
-from ..utils import logging
-from .config import OnnxConfig
+from transformers import PreTrainedModel, PreTrainedTokenizer, TensorType, TFPreTrainedModel, is_torch_available
+from transformers.file_utils import is_torch_onnx_dict_inputs_support_available
+from transformers.onnx.config import OnnxConfig
+from transformers.utils import logging
 
 
 logger = logging.get_logger(__name__)  # pylint: disable=invalid-name