class_docstr: Calculate each values percentage of a total.
  
  :param column_name:
      The name of a column containing the :class:`.Number` values.
  :param total:
      If specified, the total value for each number to be divided into. By
      default, the :class:`.Sum` of the values in the column will be used.
code: def get_computed_data_type(self, table):
      return Number()
  
file_path: agate/agate/computations/percent.py
imports: from agate.aggregations.has_nulls import HasNulls
  from agate.aggregations.sum import Sum
  from agate.computations.base import Computation
  from agate.data_types import Number
  from agate.exceptions import DataTypeError
  from agate.warns import warn_null_calculation
label_desc: Use image node_id 2 for calling the Percent obj's underlying member method code with example usage: obj.get_computed_data_type(table) and returns: Number