code: def merge(self, df: pd.DataFrame, on: str, how: str="outer", **kwargs):
          
          try:
              df = pd.merge(self.df, df, on=on, how=how, **kwargs)
              self.df = df
          except Exception as e:
              self.err(e, self.merge, "Can not merge dataframes")
docs: Set the main dataframe from the current dataframe and the passed
          dataframe
  
          :param df: the pandas dataframe to merge
          :type df: pd.DataFrame
          :param on: param for ``pd.merge``
          :type on: str
          :param how: param for ``pd.merge``, defaults to "outer"
          :type how: str, optional
          :param kwargs: keyword arguments for ``pd.merge``