Register Layout use in the Basic Usage example

[sebgrijalva]

In the readme.md there is a SquareLatticeLayout object begin imported as a special layout. But later it is never used.

from pulser.register.special_layouts import SquareLatticeLayout
# ...
# Define a register for your sequence
register = Register.square(2, spacing=5, prefix="q")
# Create a sequence for that register
sequence = Sequence(register, devices.IroiseMVP)

When I try to run the example sequence I'm getting a "Bad Request" with:

"code": 400,
  "data": {
    "body": {
      "sequence_builder": [
        "The received sequence's register was not defined from a RegisterLayout."
      ]
    }
  },
  "message": "Bad request.",
  "status": "fail"

I have been able to send the batch by changing the register creation to:

square_layout = SquareLatticeLayout(3, 3, spacing=6)
register = square_layout.define_register(0,1,2)
# Create a sequence for that register
sequence = Sequence(register, devices.IroiseMVP)

Is this something to be updated about this example? I can make a PR if so.