code: def flat_(self, col, nums=True):
          
          try:
              res = ""
              i = 0
              vals = self.df[col].tolist()
              for el in vals:
                  if nums is True:
                      res = res + str(i) + " " + el
                  else:
                      res = res + el
                  if i < (len(vals)-1):
                      res += " "
                  i += 1
              return res
          except Exception as e:
              self.err(e, "Can not flat " + col)
docs: Returns a flat representation of a column's values