text: """The code template to supply to the front end. This is what the user will
      be asked to complete and submit for grading.
  
      Do not include any imports.
  
      This is not a REPL environment so include explicit 'print' statements
      for any outputs you want to be displayed back to the user.
  
      Use triple single quotes to enclose the formatted code block.
  """
  
  challenge_code = '''def oracle_matrix(combo):
      """Return the oracle matrix for a secret combination.
      
      Args:
          combo (list[int]): A list of bits representing a secret combination.
           
      Returns: 
          array[float]: The matrix representation of the oracle.
      """
      index = np.ravel_multi_index(combo, [2]*len(combo)) # Index of solution
      my_array = np.identity(2**len(combo)) # Create the identity matrix
  
      ##################
      # YOUR CODE HERE #
      ##################
  
      # MODIFY DIAGONAL ENTRY CORRESPONDING TO SOLUTION INDEX
  
      return my_array
  '''
  