chore: import upstream snapshot with attribution

nemo/utils/dependency.py

@@ -0,0 +1,82 @@
+# Copyright (c) 2026, NVIDIA CORPORATION.  All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import importlib
+import importlib.util
+import types
+
+
+def is_module_available(*modules: str) -> bool:
+    """Check whether the given modules are installed without importing them.
+
+    This is safer than a ``try: import ...`` block because some packages have
+    side effects at import time (e.g., changing the multiprocessing start
+    method).  Use this for lightweight availability checks such as test-skip
+    decorators or conditional registration.
+
+    Args:
+        *modules: One or more top-level module names to check.
+
+    Returns:
+        ``True`` if **all** listed modules are found, ``False`` otherwise.
+    """
+    return all(importlib.util.find_spec(m) is not None for m in modules)
+
+
+def assert_optional_dependency_available(module_name: str, *, pip_name: str | None = None) -> None:
+    """Raise an ``ImportError`` if *module_name* is not installed.
+
+    Unlike :func:`import_optional_dependency` this does **not** import the
+    module — it only checks availability via :func:`is_module_available` and
+    raises with an actionable install hint on failure.  Use this for early
+    fail-fast checks (e.g., at the top of a CLI entry-point or ``__init__``).
+
+    Args:
+        module_name: The module to check (e.g. ``"lhotse"``).
+        pip_name: The pip install name if it differs from *module_name*.
+            When *None*, the top-level package name is used.
+
+    Raises:
+        ImportError: If the module is not found.
+    """
+    if not is_module_available(module_name):
+        install_name = pip_name if pip_name is not None else module_name.split(".")[0]
+        raise ImportError(
+            f"Optional dependency '{module_name}' is not installed. " f"Install it with:  pip install {install_name}"
+        )
+
+
+def import_optional_dependency(module_name: str, *, pip_name: str | None = None) -> types.ModuleType:
+    """Import an optional dependency, raising a clear error if it is not installed.
+
+    Args:
+        module_name: The module to import (e.g. ``"lhotse"`` or ``"torchaudio.transforms"``).
+        pip_name: The pip install name if it differs from *module_name*
+            (e.g. ``pip_name="Cython"`` for ``module_name="cython"``).
+            When *None*, the top-level package name is used.
+
+    Returns:
+        The imported module.
+
+    Raises:
+        ImportError: If the module cannot be imported, with an actionable
+            install hint.
+    """
+    try:
+        return importlib.import_module(module_name)
+    except ImportError:
+        install_name = pip_name if pip_name is not None else module_name.split(".")[0]
+        raise ImportError(
+            f"Optional dependency '{module_name}' is not installed. " f"Install it with:  pip install {install_name}"
+        ) from None