def dups_check(df, k):
    """checks for duplicate records in a passed in pandas dataframe based on a passed in key
    Parameters:
      df (pandas dataframe): a pandas dataframe
      k (list): columns in the dataframe that should be used to check for duplicates
    Returns:
      dups (pandas dataframe): a pandas dataframe of duplicate records based on the passed in key
        (the dups dataframe will have n - 1 records for each duplicate in the input dataframe
          where n = the number of times that duplicate occurs in the passed in dataframe)
    """
    dups = df[df.duplicated(subset = k)]
    dups = dups[k]
    return dups