Convert model from flax to TF
I am trying to convert my flax MT5 model to TensorFlow. I devised the following script using https://github.com/huggingface/transformers/issues/12545

```
from transformers import MT5Model, MT5TokenizerFast, TFMT5Model, MT5Config, FlaxT5ForConditionalGeneration

import numpy as np
import jax
import jax.numpy as jnp

pretrained = "../dumped/code-mt5-large-batch-mix/" # earlier missed the fact that there is no ckpt in this dir
tmp_path = "../dumped/code-mt5-large-batch-mix-tensorflow"

config = MT5Config.from_pretrained(pretrained, from_flax=True)
model = FlaxT5ForConditionalGeneration.from_pretrained(pretrained, config=config)
tokenizer = MT5TokenizerFast(pretrained, use_fast=True, extra_ids=160)

def to_f32(t):
    return jax.tree_map(lambda x: x.astype(jnp.float32) if x.dtype == jnp.bfloat16 else x, t)

model.params = to_f32(model.params)
model.save_pretrained(tmp_path)

model_tf = TFMT5Model.from_pretrained(tmp_path)
model_tf.save_pretrained(tmp_path)

```
However, the conversion gets aborted with this output: https://paste.ubuntu.com/p/Ynw9Tn8NC9/

According to the output, the conversion seems to require a specific file instead of the entire model directory `../dumped/code-mt5-large-batch-mix/`  (`  what():  basic_filebuf::underflow error reading the file: Is a directory
`). We are not sure if this is the case and if so what is the specific file required.

The contents of  `../dumped/code-mt5-large-batch-mix/` are:
![image](https://user-images.githubusercontent.com/43485111/125642556-933161e1-a8e3-4611-8097-9ba9f8c0e022.png)

Some help with this model conversion is much appreciated. Thanks!
At the moment we only have Flax <=> PT and TF <=> PT conversion. So you should do the following:

```python
from transformers import T5ForConditionalGeneration, MT5TokenizerFast, TFT5ForConditionalGeneration, MT5Config, FlaxT5ForConditionalGeneration

import numpy as np
import jax
import jax.numpy as jnp

pretrained = "../dumped/code-mt5-large-batch-mix/" # earlier missed the fact that there is no ckpt in this dir
tmp_path = "../dumped/code-mt5-large-batch-mix-tensorflow"

config = MT5Config.from_pretrained(pretrained, from_flax=True)
model = T5ForConditionalGeneration.from_pretrained(pretrained, config=config)
tokenizer = MT5TokenizerFast(pretrained, use_fast=True, extra_ids=160)

def to_f32(t):
    return jax.tree_map(lambda x: x.astype(jnp.float32) if x.dtype == jnp.bfloat16 else x, t)

model.params = to_f32(model.params)
model.save_pretrained(tmp_path)

model_pt = T5ForConditionalGeneration.from_pretrained(tmp_path, from_flax=True)
model_pt.save_pretrained(tmp_path)

model_tf = TFT5ForConditionalGeneration.from_pretrained(tmp_path, from_pt=True)
model_tf.save_pretrained(tmp_path)
```<|||||>Thank you!<|||||>This issue has been automatically marked as stale because it has not had recent activity. If you think this still needs to be addressed please comment on this thread.

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