diff --git a/README.md b/README.md
index b56ccc7..bc0fec9 100644
--- a/README.md
+++ b/README.md
@@ -7,6 +7,10 @@
 
 Python interpreter bindings for Deno.
 
+## Example
+
+Import any locally installed Python package, for example, `matplotlib`:
+
 ```ts
 import { python } from "https://deno.land/x/python@0.2.0/mod.ts";
 
@@ -20,6 +24,14 @@ plt.plot(xpoints, ypoints);
 plt.show();
 ```
 
+When running, you **must** specify `--allow-ffi`, `--allow-env` and `--unstable`
+flags. Alternatively, you may also just specify `-A` instead of specific
+permissions since enabling FFI effectively escapes the permissions sandbox.
+
+```shell
+deno run -A --unstable <file>
+```
+
 ## Documentation
 
 Check out the docs
@@ -29,7 +41,7 @@ Check out the docs
 
 This module uses FFI to interface with the Python interpreter's C API. So you
 must have an existing Python installation (with the shared library), which is
-something like `python39.dll`, etc.
+something like `python310.dll`, etc.
 
 Python installed from Microsoft Store does not work, as it does not contain
 shared library for interfacing with Python interpreter.
@@ -37,21 +49,16 @@ shared library for interfacing with Python interpreter.
 If the module fails to find Python, you can add the path to the Python in the
 `DENO_PYTHON_PATH` environment variable.
 
+`DENO_PYTHON_PATH` if set, must point to full path including the file name of
+the Python dynamic library, which is like `python310.dll` (Windows),
+`libpython310.dylib` (macOS) and `libpython310.so` (Linux) depending on
+platform.
+
 ## Maintainers
 
 - DjDeveloper ([@DjDeveloperr](https://github.com/DjDeveloperr))
 - Elias Sjögreen ([@eliassjogreen](https://github.com/eliassjogreen))
 
-## Permission Table
-
-| Permission Needed | Reason                                         |
-| ----------------- | ---------------------------------------------- |
-| `--allow-env`     | For finding the location of the python library |
-| `--allow-run`     | For finding the location of the python library |
-| `--allow-read`    | For reading the library                        |
-| `--allow-ffi`     | It uses FFI to interact with python            |
-| `--unstable`      | It's unstable because it uses FFI              |
-
 ## Other
 
 ### Contribution
diff --git a/src/python.ts b/src/python.ts
index f8745f6..11dccda 100644
--- a/src/python.ts
+++ b/src/python.ts
@@ -135,7 +135,7 @@ export function kw(
  * ```
  */
 export class Callback {
-  unsafe: Deno.UnsafeCallback;
+  unsafe;
 
   constructor(public callback: PythonJSCallback) {
     this.unsafe = new Deno.UnsafeCallback(