cannot import name 'schema_json_of' from 'pydantic'

[numb3r3]

We need explicitly add the dependency pydantic>=1.9.0 in setup.py. With pydantic==1.8.2, the following error is throw

$ pytest tests/unit/test_pydantic.py

cls = <class 'docarray.array.document.DocumentArray'>, indent = 2

    @classmethod
    def get_json_schema(cls, indent: int = 2) -> str:
        """Return a JSON Schema of DocumentArray class."""
>       from pydantic import schema_json_of
E       ImportError: cannot import name 'schema_json_of' from 'pydantic' (/Users/fengwang/.pyenv/versions/3.8.3/lib/python3.8/site-packages/pydantic/__init__.cpython-38-darwin.so)

docarray/array/mixins/pydantic.py:13: ImportError