def default_value(self, use_server: bool = False) -> Optional[Dict]:
        """
        Returns a FieldInfo instance with populated default
        (static) or default_factory (function).
        If the field is a autoincrement primary key the default is None.
        Otherwise field have to has either default, or default_factory populated.

        If all default conditions fail None is returned.

        Used in converting to pydantic FieldInfo.

        :param use_server: flag marking if server_default should be
        treated as default value, default False
        :type use_server: bool
        :return: returns a call to pydantic.Field
        which is returning a FieldInfo instance
        :rtype: Optional[pydantic.FieldInfo]
        """
        if self.is_auto_primary_key():
            return dict(default=None)
        if self.has_default(use_server=use_server):
            default = (
                self.ormar_default
                if self.ormar_default is not None
                else self.server_default
            )
            if callable(default):
                return dict(default_factory=default)
            return dict(default=default)
        return None

        Returns a FieldInfo instance with populated default
        (static) or default_factory (function).
        If the field is a autoincrement primary key the default is None.
        Otherwise field have to has either default, or default_factory populated.

        If all default conditions fail None is returned.

        Used in converting to pydantic FieldInfo.

        :param use_server: flag marking if server_default should be
        treated as default value, default False
        :type use_server: bool
        :return: returns a call to pydantic.Field
        which is returning a FieldInfo instance
        :rtype: Optional[pydantic.FieldInfo]
        
ormar/fields/base.py