code: def _set_noconvert_columns(self):
          
          names = self.orig_names
          if self.usecols_dtype == 'integer':
              # A set of integers will be converted to a list in
              # the correct order every single time.
              usecols = list(self.usecols)
              usecols.sort()
          elif (callable(self.usecols) or
                  self.usecols_dtype not in ('empty', None)):
              # The names attribute should have the correct columns
              # in the proper order for indexing with parse_dates.
              usecols = self.names[:]
          else:
              # Usecols is empty.
              usecols = None
  
          def _set(x):
              if usecols is not None and is_integer(x):
                  x = usecols[x]
  
              if not is_integer(x):
                  x = names.index(x)
  
              self._reader.set_noconvert(x)
  
          if isinstance(self.parse_dates, list):
              for val in self.parse_dates:
                  if isinstance(val, list):
                      for k in val:
                          _set(k)
                  else:
                      _set(val)
  
          elif isinstance(self.parse_dates, dict):
              for val in self.parse_dates.values():
                  if isinstance(val, list):
                      for k in val:
                          _set(k)
                  else:
                      _set(val)
  
          elif self.parse_dates:
              if isinstance(self.index_col, list):
                  for k in self.index_col:
                      _set(k)
              elif self.index_col is not None:
                  _set(self.index_col)
docs: Set the columns that should not undergo dtype conversions.
  
          Currently, any column that is involved with date parsing will not
          undergo such conversions.