Add InferenceService resource (#1886)

* Add InferenceService resource

* Fix str formatting

ocp_resources/inference_service.py

@@ -0,0 +1,50 @@
+from typing import Optional, Dict, Any
+
+from ocp_resources.resource import NamespacedResource, MissingRequiredArgumentError
+
+
+class InferenceService(NamespacedResource):
+    """
+    https://github.com/kserve/kserve/blob/master/pkg/apis/serving/v1beta1/inference_service.go
+    """
+
+    api_group: str = NamespacedResource.ApiGroup.SERVING_KSERVE_IO
+
+    def __init__(
+        self,
+        predictor: Optional[Dict[str, Any]] = None,
+        explainer: Optional[Dict[str, Any]] = None,
+        transformer: Optional[Dict[str, Any]] = None,
+        **kwargs,
+    ):
+        """
+        InferenceService object
+
+        Args:
+            predictor (Optional[Dict[str, Any]], mandatory if yaml_file is not provided): Defines the model serving spec.
+            explainer (Optional[Dict[str, Any]]): Defines the model explanation service spec.
+            transformer (Optional[Dict[str, Any]]): Defines the pre/post processing before and after the predictor call.
+        """
+        super().__init__(
+            **kwargs,
+        )
+        self.predictor = predictor
+        self.explainer = explainer
+        self.transformer = transformer
+
+    def to_dict(self) -> None:
+        super().to_dict()
+        if not self.yaml_file:
+            if not self.predictor:
+                raise MissingRequiredArgumentError(argument="predictor")
+
+            self.res["spec"] = {}
+            _spec = self.res["spec"]
+
+            _spec["predictor"] = self.predictor
+
+            if self.explainer:
+                _spec["explainer"] = self.explainer
+
+            if self.transformer:
+                _spec["transformer"] = self.transformer