Create is_pip() function (ultralytics#3391)

Returns `True` if file is part of pip package. Useful for contextual behavior modification.

```python
def is_pip():
    # Is file in a pip package?
    return 'site-packages' in Path(__file__).absolute().parts
```

utils/general.py

@@ -53,19 +53,24 @@ def get_latest_run(search_dir='.'):
 
 
 def is_docker():
-    # Is environment a Docker container
+    # Is environment a Docker container?
     return Path('/workspace').exists()  # or Path('/.dockerenv').exists()
 
 
 def is_colab():
-    # Is environment a Google Colab instance
+    # Is environment a Google Colab instance?
     try:
         import google.colab
         return True
     except Exception as e:
         return False
 
 
+def is_pip():
+    # Is file in a pip package?
+    return 'site-packages' in Path(__file__).absolute().parts
+
+
 def emojis(str=''):
     # Return platform-dependent emoji-safe version of string
     return str.encode().decode('ascii', 'ignore') if platform.system() == 'Windows' else str