[{'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:b"import numpy as np\\n#train=train[(train.age > 14) & (train.age < 110)]# modele sadece 14 yandan byk ve 110 yandan kkleri dahil edebilirim.\\n#test=test[(test.age > 14) & (test.age < 110)]\\ntrain[(train.age < 14) & (train.age > 110)]=np.nan\\ntest[(test.age < 14) & (test.age > 110)]=np.nan\\ntrain[\'age\'].fillna(train[\'age\'].mean(), inplace=True)\\ntest[\'age\'].fillna(train[\'age\'].mean(), inplace=True)"'}, {'role': 'assistant', 'content': 'data_preprocessing'}]