Feature implement bpm device

[gubaidulinvadim]

First try at BPM implementation. Following Issue #6 and some discussions with Jean-Luc. I've only added the simplest tests for now.

[JeanLucPons]

2 things:

• You can remove the hardware part. For model without needed conversion or extra calculation we will do as for magnet using identity bpm model.
• It would be nice to test attached field and initialize them to None in __init__() i.e.

    @property
    def tilt(self) -> RWBpmTiltScalar:
        if self.__tilt is None:
            raise PyAMLException(f"{str(self)} does not support tilt")
        return self.__tilt

[gubaidulinvadim]

OK, I will correct. I understood that the hardware part can be skipped only yesterday by looking at your RF device implementation.

[JeanLucPons]

According to @gupichon modifications, an other field than FamName can be used for elements identification.
So you should pass it to the construct of your RBpmArray and use this field.

index = self.lattice.get_refpts(self.element.FamName)

[JeanLucPons]

Unfortunately I'm not sure that get_refpts() can be used to select on an arbitrary AT field.
You may need to extract the index at each call.

[JeanLucPons]

I think a simple mods like below should be ok.

    def get(self) -> np.array:
        index = self.lattice.index(self.element)
        _, orbit = at.find_orbit(self.lattice, refpts=index)
        return orbit[0, [0, 2]]

[JeanLucPons]

May be remove the debug trace

print(self.__BPMS.keys())

[JeanLucPons]

Nice works. Thanks
Just few details above !

[gubaidulinvadim]

I've made the corrections and also added a test with a nonzero orbit by setting one of the corrector magnet strength to 1e-6 in the test. FYI, I've created an issue in tango-pyaml python-accelerator-middle-layer/tango-pyaml#21 but I'm not sure if it originates in tango-pyaml or in pyaml itself. If I use type: tango.pyaml.attribute_read_only the configuration part fails, with type: tango.pyaml.attribute everything works.

[JeanLucPons]

I've made the corrections and also added a test with a nonzero orbit by setting one of the corrector magnet strength to 1e-6 in the test. FYI, I've created an issue in tango-pyaml python-accelerator-middle-layer/tango-pyaml#21 but I'm not sure if it originates in tango-pyaml or in pyaml itself. If I use type: tango.pyaml.attribute_read_only the configuration part fails, with type: tango.pyaml.attribute everything works.

Yes I think there is a bug in attribute_read_only that prevents to use get().
We will fix this ASAP
Thanks for the updates