initial commit, add gello software code and instructions

gello/dm_control_tasks/mjcf_utils.py

@@ -0,0 +1,23 @@
+from pathlib import Path
+from typing import List
+
+from dm_control import mjcf
+
+# Path to the root of the project.
+_PROJECT_ROOT: Path = Path(__file__).parent.parent.parent
+
+# Path to the Menagerie submodule.
+MENAGERIE_ROOT: Path = _PROJECT_ROOT / "third_party" / "mujoco_menagerie"
+
+
+def safe_find_all(
+    root: mjcf.RootElement,
+    feature_name: str,
+    immediate_children_only: bool = False,
+    exclude_attachments: bool = False,
+) -> List[mjcf.Element]:
+    """Find all given elements or throw an error if none are found."""
+    features = root.find_all(feature_name, immediate_children_only, exclude_attachments)
+    if not features:
+        raise ValueError(f"No {feature_name} found in the MJCF model.")
+    return features