docs: def get_database_columns(self, tables=None, database=None):
          """Retrieve a dictionary of columns."""
          # Get table data and columns from source database
          source = database if database else self.database
          tables = tables if tables else self.tables
          return {tbl: self.get_columns(tbl) for tbl in tqdm(tables, total=len(tables),
                                                             desc='Getting {0} columns'.format(source))}