def pre_process_medications(df):
    """
    Input:        Pandas dataframe
    Output:       Pandas dataframe
    Description:  Group all rows with patient characteristics (age, sex, race) into a single row, keyed by 
                  'encounter_id'. The nueric value represents the number of times a type of medication was
                  administered to a patient.    
    """
    
    # The query only pulls medication data from the 13 hours prior to an RRT event
    # Or 13 hours prior to the midpoint of an encounter for a nonRRT encounter
    meds = df.drop(['multum_category_id', 'orig_order_dt_tm'], axis=1)
    return meds.groupby('encntr_id').sum()