code: def types_(self, col: str) -> pd.DataFrame:
          
          cols = self.df.columns.values
          all_types = {}
          for col in cols:
              local_types = []
              for i, val in self.df[col].iteritems():
                  #print(i, val, type(val))
                  t = type(val).__name__
                  if t not in local_types:
                      local_types.append(t)
              all_types[col] = (local_types, i)
          df = pd.DataFrame(all_types, index=["type", "num"])
          return df
docs: Display types of values in a column
  
          :param col: column name
          :type col: str
          :return: a pandas dataframe
          :rtype: pd.DataFrame
  
          :example: ``ds.types_("Col 1")``