[{'role': 'system', 'content': "You are an expert in machine learning and your task is to classify code snippets into one of the following categories: ['helper_functions', 'load_data', 'data_exploration', 'data_preprocessing', 'evaluation', 'modelling', 'prediction', 'result_visualization', 'save_results', 'comment_only']."}, {'role': 'user', 'content': 'Identify the single most appropriate category to which the provided code belongs. Provide your response as a single category label without any additional information, commentary, or personal opinions.\\nPython Code:from sklearn import preprocessing\ndef normalize(x):\n"""\nNormalize a list of sample image data in the range of 0 to 1\n: x: List of image data.  The image shape is (32, 32, 3)\n: return: Numpy array of normalize data\n"""\nreturn x/255\n"""\nDON\'T MODIFY ANYTHING IN THIS CELL THAT IS BELOW THIS LINE\n"""\ntests.test_normalize(normalize)'}, {'role': 'assistant', 'content': 'data_preprocessing'}]