code: def nan_empty(self, col: str):
          
          try:
              self.df[col] = self.df[col].replace('', nan)
              self.ok("Filled empty values with nan in column " + col)
          except Exception as e:
              self.err(e, "Can not fill empty values with nan")
docs: Fill empty values with NaN values
  
          :param col: name of the colum
          :type col: str
  
          :example: ``ds.nan_empty("mycol")``