def determine_choice_type_override(field_data, field_def)
      result = nil
      if field_data.kind_of?(Hash) and field_def.include?(:choices)
        result = determine_choice(field_data, field_def[:choices])
      end
      return result
    end
def determine_choice_type_override(field_data, field_def)
      result = nil
      if field_data.kind_of?(Hash) and field_def.include?(:choices)
        result = determine_choice(field_data, field_def[:choices])
      end
      return result
    end
Determines a choice type override for for the field. Returns nil if no
 override found.