parameters: (self, keys)
return_statement: return result
docstring: Returns a new DataFrame with a subset of columns.
  
      Args:
        keys: A list of strings. Each should be the name of a column in the
          DataFrame.
      Returns:
        A new DataFrame containing only the specified columns.
docstring_summary: Returns a new DataFrame with a subset of columns.
docstring_tokens: Returns a new DataFrame with a subset of columns .
function: def select_columns(self, keys):
      """Returns a new DataFrame with a subset of columns.
  
      Args:
        keys: A list of strings. Each should be the name of a column in the
          DataFrame.
      Returns:
        A new DataFrame containing only the specified columns.
      """
      result = type(self)()
      for key in keys:
        result[key] = self._columns[key]
      return result
function_tokens: def select_columns ( self , keys ) : result = type ( self ) ( ) for key in keys : result [ key ] = self . _columns [ key ] return result