- Update to version 1.4
* rename Schema to Field, make it a function to placate mypy
* Implement root_validator and rename root errors from __obj__ to __root__
* Added initvars support to post_init_post_parse
* complete rewrite of URL parsing logic
* BaseSettings now uses the special env settings to define which
environment variables to read, not aliases
* add support for assert statements inside validators
* Change the precedence of aliases so child model aliases override
parent aliases, including using alias_generator
* Add a mypy plugin for type checking BaseModel.__init__ and more
* Add support for typing.Literal for Python 3.8
* Add a ByteSize type for converting byte string (1GB) to plain bytes
* Add support for required Optional with name: Optional[AnyType] = Field(...)
and refactor ModelField creation to preserve required parameter value
* Add __eq__ to SecretStr and SecretBytes to allow "value equals"
* Add support for nested generic models
* alias precedence logic changed so aliases on a field always take
priority over an alias from alias_generator
* many more fixes and improvements