Takes a list of dataframes, each of which contains a column with the same name and, for each dataframe, removes rows where the value in the common column has already occured in a previous row of that dataframe.
drop_repeated(df_list, column_name)A list of dataframes. Each dataframe should contain a column
whose name matches column_name
The name of the column from which to remove duplicates.
a list of dataframes with no repeated values in column_name