class_docstr: Defines a single training or test example.
  
  Stores each column of the example as an attribute.
code: def fromCSV(cls, data, fields, field_to_index=None):
      if field_to_index is None:
          return cls.fromlist(data, fields)
      else:
          assert isinstance(fields, dict)
          data_dict = {
              f: data[idx] for f, idx in field_to_index.items()
          }
          return cls.fromdict(data_dict, fields)
  
file_path: pytext/pytext/legacy/data/example.py
imports: import json
  from functools import reduce
label_desc: Use image node_id 3 for calling the Example obj's underlying member method code with example usage: obj.fromCSV(cls, data, fields, field_to_index) and returns: cls, cls