class_docstr: Calculate the sum of a column.
  
  :param column_name:
      The name of a column containing :class:`.Number` data.
code: def validate(self, table):
      column = table.columns[self._column_name]
  
      if not isinstance(column.data_type, (Number, TimeDelta)):
          raise DataTypeError(
              "Sum can only be applied to columns containing Number or TimeDelta data."
          )
  
file_path: agate/agate/aggregations/sum.py
imports: import datetime
  from agate.aggregations.base import Aggregation
  from agate.data_types import Number, TimeDelta
  from agate.exceptions import DataTypeError
label_desc: Use image node_id 3 for calling the Sum obj's underlying member method code with example usage: obj.validate(table) without return types