updates streaming guide with note about usage field

examples/How_to_stream_completions.ipynb

@@ -1,6 +1,7 @@
 {
  "cells": [
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@@ -14,8 +15,14 @@
     "\n",
     "To stream completions, set `stream=True` when calling the Completions endpoint. This will return an object that streams back text as [data-only server-sent events](https://app.mode.com/openai/reports/4fce5ba22b5b/runs/f518a0be4495).\n",
     "\n",
+    "## Downsides\n",
+    "\n",
     "Note that using `stream=True` in a production application makes it more difficult to moderate the content of the completions, which has implications for [approved usage](https://beta.openai.com/docs/usage-guidelines).\n",
     "\n",
+    "Another small drawback of streaming responses is that the response no longer includes the `usage` field to tell you how many tokens were consumed. After receiving and combining all of the responses, you can calculate this yourself using [`tiktoken`](How_to_count_tokens_with_tiktoken.ipynb).\n",
+    "\n",
+    "## Example code\n",
+    "\n",
     "Below is a Python code example of how to receive streaming completions."
    ]
   },
@@ -31,10 +38,11 @@
    ]
   },
   {
+   "attachments": {},
    "cell_type": "markdown",
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    "source": [
-    "## A typical completion request\n",
+    "### A typical completion request\n",
     "\n",
     "With a typical Completions API call, the text is first computed and then returned all at once."
    ]
@@ -80,10 +88,11 @@
    ]
   },
   {
+   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "## A streaming completion request\n",
+    "### A streaming completion request\n",
     "\n",
     "With a streaming Completions API call, the text is sent back via a series of events. In Python, you can iterate over these events with a `for` loop."
    ]
@@ -328,10 +337,11 @@
    ]
   },
   {
+   "attachments": {},
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "## Time comparison\n",
+    "### Time comparison\n",
     "\n",
     "In the example above, both requests took about 7 seconds to fully complete.\n",
     "\n",
@@ -355,7 +365,7 @@
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-   "version": "3.9.9"
+   "version": "3.9.9 (main, Dec  7 2021, 18:04:56) \n[Clang 13.0.0 (clang-1300.0.29.3)]"
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