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.
docstr: :returns:
      :class:`int`.
code: def run(self, table):
      """
      :returns:
          :class:`int`.
      """
      column = table.columns[self._column_name]
  
      lens = [len(d) for d in column.values_without_nulls()]
  
      if not lens:
          return Decimal("0")
  
      return Decimal(max(lens))
  
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 4 for calling the MaxLength obj's underlying member method code with example usage: obj.run(table) and returns: Decimal, Decimal