Hi good morning dear colleagues, I am trying to evolve a system with six coherent states as input to three beamsplitters and I am facing the following errors described in the images below. How would I make this system evolve correctly?

```
# import numpy as np
from mrmustard.lab import *
vac = Vacuum(num_modes=2) # 2-mode vacuum state
coh0 = Coherent(x=-0.1, y=-0.4) # coh state |-alpha> with alpha = -0.1 - 0.4j
coh1 = Coherent(x=0.1, y=-0.4) # coh state |alpha> with alpha = 0.1 - 0.4j
sq = SqueezedVacuum(r=0.5) # squeezed vacuum state
g = Gaussian(num_modes=2) # 2-mode Gaussian state with zero means
fock4 = Fock(4) # fock state |4>
D = Dgate(x=1.0, y=-0.4) # Displacement by 1.0 along x and -0.4 along y
S = Sgate(r=0.5) # Squeezer with r=0.5
BS = BSgate(theta=np.pi/4) # 50/50 beam splitter
S2 = S2gate(r=0.5) # two-mode squeezer
MZ = MZgate(phi_a=0.3, phi_b=0.1) # Mach-Zehnder interferometer
I = Interferometer(8) # 8-mode interferometer
L = Attenuator(0.5) # pure lossy channel with 50% transmissivity
A = Amplifier(gain=2.0, nbar=1.0) # noisy amplifier with 200% gain
## Primeira bateria de BS
Coherent(x=[1.0, 2.0], y=[-1.0, -2.0]) >> BS[0,1]
Coherent(x=[1.0, 2.0], y=[-1.0, -2.0]) >> BS[2,3]
Coherent(x=[1.0, 2.0], y=[-1.0, -2.0]) >> BS[4,5]
## Segunda bateria de BS
Coherent(x=[1.0, 2.0], y=[-1.0, -2.0]) >> BS[3,5]
Coherent(x=[1.0, 2.0], y=[-1.0, -2.0]) >> BS[1,6]
Coherent(x=[1.0, 2.0], y=[-1.0, -2.0]) >> BS[2,4]
```

If you want help with diagnosing an error, please put the full error message below:

```
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
Cell In[6], line 4
1 ## Primeira bateria de BS
3 Coherent(x=[1.0, 2.0], y=[-1.0, -2.0]) >> BS[0,1]
----> 4 Coherent(x=[1.0, 2.0], y=[-1.0, -2.0]) >> BS[2,3]
5 Coherent(x=[1.0, 2.0], y=[-1.0, -2.0]) >> BS[4,5]
File ~\anaconda3\lib\site-packages\mrmustard\lab\abstract\state.py:500, in State.__rshift__(self, other)
496 if issubclass(other.__class__, State):
497 raise TypeError(
498 f"Cannot apply {other.__class__.__qualname__} to a state. Are you looking for the << operator?"
499 )
--> 500 return other.primal(self)
File ~\anaconda3\lib\site-packages\mrmustard\lab\abstract\transformation.py:56, in Transformation.primal(self, state)
47 r"""Applies ``self`` (a ``Transformation``) to other (a ``State``) and returns the transformed state.
48
49 Args:
(...)
53 State: the transformed state
54 """
55 if state.is_gaussian:
---> 56 new_state = self.transform_gaussian(state, dual=False)
57 else:
58 new_state = self.transform_fock(state, dual=False)
File ~\anaconda3\lib\site-packages\mrmustard\lab\abstract\transformation.py:103, in Transformation.transform_gaussian(self, state, dual)
93 r"""Transforms a Gaussian state into a Gaussian state.
94
95 Args:
(...)
100 State: the transformed state
101 """
102 X, Y, d = self.XYd if not dual else self.XYd_dual
--> 103 cov, means = gaussian.CPTP(state.cov, state.means, X, Y, d, state.modes, self.modes)
104 new_state = State(
105 cov=cov, means=means, modes=state.modes, _norm=state.norm
106 ) # NOTE: assumes modes don't change
107 return new_state
File ~\anaconda3\lib\site-packages\mrmustard\physics\gaussian.py:432, in CPTP(cov, means, X, Y, d, state_modes, transf_modes)
411 r"""Returns the cov matrix and means vector of a state after undergoing a CPTP channel.
412
413 Computed as ``cov = X \cdot cov \cdot X^T + Y`` and ``d = X \cdot means + d``.
(...)
429 Tuple[Matrix, Vector]: the covariance matrix and the means vector of the state after the CPTP channel
430 """
431 if not set(transf_modes).issubset(state_modes):
--> 432 raise ValueError(
433 f"The channel should act on a subset of the state modes ({transf_modes} is not a subset of {state_modes})"
434 )
435 # if single-mode channel, apply to all modes indicated in `modes`
436 if X is not None and X.shape[-1] == 2:
ValueError: The channel should act on a subset of the state modes ([2, 3] is not a subset of [0, 1])
```

conda 23.3.1

mrmustard 0.3.0

numpy 1.23.5