[{'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:import keras\nimport numpy as np\nimport pandas as pd\nfrom keras.models import Sequential\nfrom keras.layers.core import Dense, Dropout, Activation\nfrom keras.layers.normalization import BatchNormalization\nfrom keras.layers.advanced_activations import PReLU\nfrom keras.utils import np_utils, generic_utils\nfrom sklearn.preprocessing import StandardScaler\nnp.random.seed(1337) # for reproducibility\ndef preprocess_data(X, scaler=None):\nif not scaler:\nscaler = StandardScaler()\nscaler.fit(X)\nX = scaler.transform(X)\nreturn X, scaler'}, {'role': 'assistant', 'content': 'data_preprocessing'}]