The best data augmentation methods for text input in Keras include synonym replacement (WordNet), back-translation, random word insertion/deletion, paraphrasing with LLMs, and contextual embeddings (Word2Vec, BERT) to generate diverse training samples.
Here is the code snippet given below:

In the above code we are using the following techniques:
- 
Synonym Replacement (WordNet/NLPAug): 
- Replaces words with synonyms while preserving sentence meaning.
 
- 
Back-Translation (Helsinki-NLP): 
- Translates text to another language and back for natural variation.
 
- 
Random Word Insertion & Deletion: 
- Adds noise and diversity to prevent overfitting.
 
- 
Contextual Embedding Augmentation (BERT/Word2Vec): 
- Replaces words with semantically similar embeddings for realistic variations.
 
- 
Paraphrasing with LLMs (GPT-3, T5, Pegasus): 
- Generates syntactically diverse yet semantically equivalent sentences.
 
Hence, using synonym replacement, back-translation, word manipulations, and embedding-based transformations significantly enhances text dataset diversity for robust Keras models.