To create an API key, in your Console, click Navigation menu > APIs & services > Credentials.

Then click + CREATE CREDENTIALS.

In the drop down menu, select API key:

Next, copy the key you just generated. Then click CLOSE. Now that you have an API key, save it to an environment variable to avoid having to insert the value of your API key in each request.

In Cloud Shell run the following. Be sure to replace  with the key you just copied:

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