implement load placeholder plugin

client/ayon_houdini/plugins/workfile_build/load_placeholder.py

@@ -0,0 +1,52 @@
+from ayon_core.pipeline.workfile.workfile_template_builder import (
+    LoadPlaceholderItem,
+    PlaceholderLoadMixin,
+)
+
+from ayon_houdini.api.workfile_template_builder import (
+    HoudiniPlaceholderPlugin
+)
+from ayon_houdini.api.lib import read, lsattr
+
+
+class HoudiniPlaceholderLoadPlugin(
+    HoudiniPlaceholderPlugin, PlaceholderLoadMixin
+):
+    """Workfile template plugin to create "load placeholders".
+
+    "load placeholders" will be replaced by AYON products.
+
+    """
+
+    identifier = "ayon.load.placeholder"
+    label = "Houdini Load"
+
+    def populate_placeholder(self, placeholder):
+        self.populate_load_placeholder(placeholder)
+
+    def repopulate_placeholder(self, placeholder):
+        self.populate_load_placeholder(placeholder)
+
+    def get_placeholder_options(self, options=None):
+        return self.get_load_plugin_options(options)
+
+    def get_placeholder_node_name(self, placeholder_data):
+
+        node_name = "{}_{}".format(
+            self.identifier.replace(".", "_"),
+            placeholder_data["product_name"]
+        )
+        return node_name
+
+    def collect_placeholders(self):
+        output = []
+        load_placeholders = self.collect_scene_placeholders()
+
+        for node in load_placeholders:
+            placeholder_data = read(node)
+            output.append(
+                LoadPlaceholderItem(node.path(), placeholder_data, self)
+            )
+
+        return output
+