code: def check_df(self, df):
          
          if isinstance(df, pd.DataFrame):
              if not df.index.is_unique:
                  repeats = df.index[df.index.duplicated()].values
                  msg = "Index values must be unique but aren't. The following entries appear more than once: {}".format(repeats)
                  self.logger.error(msg)
                  raise Exception("GCToo GCToo.check_df " + msg)
              if not df.columns.is_unique:
                  repeats = df.columns[df.columns.duplicated()].values
                  msg = "Columns values must be unique but aren't. The following entries appear more than once: {}".format(repeats)
                  raise Exception("GCToo GCToo.check_df " + msg)
              else:
                  return True
          else:
              msg = "expected Pandas DataFrame, got something else:  {}  of type:  {}".format(df, type(df))
              self.logger.error(msg)
              raise Exception("GCToo GCToo.check_df " + msg)
docs: Verifies that df is a pandas DataFrame instance and
          that its index and column values are unique.