input: from typing import Any
  
  def classify_string(input_string: str) -> Any:
      """ Categorizes user input using a machine learning classifier.
      >>> classify_string("example_input")
      'example_output'
      >>> classify_string("another_input")
      'another_output'
      """
      
      # Feature extraction and transformation from string to numeric
      features = . . .
  
      # Create an instance of the classifier 
      model = MultinomialNB()
  
      # Train the classifier on the data
      model.fit(data, target)
  
      # Make a prediction based on the input
      prediction = model.predict([features])
  
      # Return the prediction
      return prediction
output:     # Feature extraction and transformation from string to numeric
      features = [ord(char) for char in input_string]
  
      # Create an instance of the classifier 
      model = MultinomialNB()
  
      # Train the classifier on the data
      data = [[ord(char) for char in "example_input"], [ord(char) for char in "another_input"]]
      target = ['example_output', 'another_output']
      model.fit(data, target)
  
      # Make a prediction based on the input
      prediction = model.predict([features])
  
      # Return the prediction
      return prediction[0]