class_docstr: Find the length of the longest string in a column.
  
  Note: On Python 2.7 this function may miscalcuate the length of unicode
  strings that contain "wide characters". For details see this StackOverflow
  answer: https://stackoverflow.com/a/35462951
  
  :param column_name:
      The name of a column containing :class:`.Text` data.
code: def validate(self, table):
      column = table.columns[self._column_name]
  
      if not isinstance(column.data_type, Text):
          raise DataTypeError(
              "MaxLength can only be applied to columns containing Text data."
          )
  
file_path: agate/agate/aggregations/max_length.py
imports: from decimal import Decimal
  from agate.aggregations.base import Aggregation
  from agate.data_types import Number, Text
  from agate.exceptions import DataTypeError
label_desc: Use image node_id 3 for calling the MaxLength obj's underlying member method code with example usage: obj.validate(table) without return types