Ingesting a DTO with reserved word keys using dataclasses (JSONWizard helper class from the dataclass-wizard package). One way is to name all the classes manually, but better is to set the letter case to 'PASCAL' which will 'upper camel case' them. The only cases this won't work for are if "True", "False", or "None" are keys in the DTO.

json_field_demo.py

from __future__ import annotations
from dataclasses import dataclass, field
from datetime import date
from dataclass_wizard import JSONWizard, json_field

@dataclass
class Lesson(JSONWizard):
    _def: str = json_field('def', all=True)
    _if: date = json_field('if', all=True)

@dataclass
class ClassInfo(JSONWizard):
    _class: str = json_field('class', all=True)
    _for: str = json_field('for', all=True)
    _and: str = json_field('and', all=True)
    _from: date = json_field('from', all=True)
    values: list[Lesson] = field(default_factory=list)

json_string = """
{
  "class": "Math",
  "for": "Beginners",
  "and": "Intermediate",
  "from": "2023-05-25",
  "values": [
    {
      "def": "Geometry",
      "if": "2023-06-01"
    },
    {
      "def": "Algebra",
      "if": "2023-07-01"
    }
  ]
}
"""

class_info = ClassInfo.from_json(json_string)

json_field_demo_alt.py

from __future__ import annotations

from dataclasses import dataclass, field
from datetime import date

from dataclass_wizard import JSONWizard


@dataclass
class Lesson(JSONWizard):
    class Meta(JSONWizard.Meta):
        key_transform_with_load = "PASCAL"

    Def: str
    If: date


@dataclass
class ClassInfo(JSONWizard):
    class Meta(JSONWizard.Meta):
        key_transform_with_load = "PASCAL"

    Class: str
    For: str
    And: str
    From: date
    Values: list[Lesson] = field(default_factory=list)


json_string = """
{
  "class": "Math",
  "for": "Beginners",
  "and": "Intermediate",
  "from": "2023-05-25",
  "values": [
    {"def": "Geometry", "if": "2023-06-01"},
    {"def": "Algebra", "if": "2023-07-01"}
  ]
}
"""

class_info = ClassInfo.from_json(json_string)

py_rw.json

{
  "class": "Math",
  "for": "Beginners",
  "and": "Intermediate",
  "from": "2023-05-25",
  "values": [
    {
      "def": "Geometry",
      "if": "2023-06-01"
    },
    {
      "def": "Algebra",
      "if": "2023-07-01"
    }
  ]
}