code: def get_input(self, name, ds):
          
          columns = self.inputs.get(name)
          df = ds.get_dataframe()
  
          # set defaults
          for column in columns:
              if column not in df.columns:
                  df[column] = self.defaults.get(column)
  
          return df[columns]
docs: Retrieves the content of an input given a DataSource. The input acts like a filter over the outputs of the DataSource.
  
          Args:
              name (str): The name of the input.
              ds (openflow.DataSource): The DataSource that will feed the data.
  
          Returns:
              pandas.DataFrame: The content of the input.