[REQ][Python-flask] Support type hints

Created by: nmoreaud

Would it be possible to add support for type hints in python flask generator? It would help me to reduce the number of bugs in my application.

Ex replace this:

class ConnectionInfo(Model):
    """NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).

    Do not edit the class manually.
    """

    def __init__(self, name=None):  # noqa: E501
        """ConnectionInfo - a model defined in OpenAPI

        :param name: The name of this ConnectionInfo.  # noqa: E501
        :type name: str
        """
        self.openapi_types = {
            'name': str
        }

        self.attribute_map = {
            'name': 'name'
        }

        self.name = name

    @property
    def name(self):
        """Gets the name of this ConnectionInfo.

        Human-readable name of the connection.  # noqa: E501

        :return: The name of this ConnectionInfo.
        :rtype: str
        """
        return self._name

    @name.setter
    def name(self, name):
        """Sets the name of this ConnectionInfo.

        Human-readable name of the connection.  # noqa: E501

        :param name: The name of this ConnectionInfo.
        :type name: str
        """

        self._name = name

with:

class ConnectionInfo(Model):
    """NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).

    Do not edit the class manually.
    """

    def __init__(self, id:str=None, name=None, references=None, db_info=None):  # noqa: E501
        """ConnectionInfo - a model defined in OpenAPI"""
        self.openapi_types = {
            'name': str
        }

        self.attribute_map = {
            'name': 'name'
        }

        self.name = name

    @property
    def name(self) -> str:
        """Gets the name of this ConnectionInfo.
        Human-readable name of the connection."""
        return self._name

    @name.setter
    def name(self, name: str):
        """Sets the name of this ConnectionInfo.
        Human-readable name of the connection. """
        self._name = name