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* **function**: is the function below the "decorator" (below `@app.get("/")`).

{* ../../docs_src/first_steps/tutorial001.py hl[7] *}

This is a Python function.

It will be called by **FastAPI** whenever it receives a request to the URL "`/`" using a `GET` operation.

In this case, it is an `async` function.

---

You could also define it as a normal function instead of `async def`:

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   */
  Throwable failureCause();

  /**
   * Registers a {@link Listener} to be {@linkplain Executor#execute executed} on the given
   * executor. The listener will have the corresponding transition method called whenever the
   * service changes state. The listener will not have previous state changes replayed, so it is
   * suggested that listeners are added before the service starts.
   *

#### Password hashing { #password-hashing }

"Hashing" means: converting some content (a password in this case) into a sequence of bytes (just a string) that looks like gibberish.

Whenever you pass exactly the same content (exactly the same password) you get exactly the same gibberish.

But you cannot convert from the gibberish back to the password.

##### Why use password hashing { #why-use-password-hashing }

      }
    }
  }

  /**
   * Returns a hash code, having the same bit length as each of the input hash codes, that combines
   * the information of these hash codes in an ordered fashion. That is, whenever two equal hash
   * codes are produced by two calls to this method, it is <i>as likely as possible</i> that each
   * was computed from the <i>same</i> input hash codes in the <i>same</i> order.
   *

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