String representation for Accelerator object

[gubaidulinvadim]

Description, motivation and use case
String representation is missing for the Accelerator object. One should be able to see, for example, what control modes are available and some common properties between the modes, like the energy.

Proposed solution
Implement repr and/or str for Accelerator object.

Example
The example demonstrates the issue, not the solution.

In [4]: sr
Out[4]: <pyaml.accelerator.Accelerator at 0x75e725327e30>

In [5]: print(sr)
<pyaml.accelerator.Accelerator object at 0x75e725327e30>

In [6]: sr.design
Out[6]: Simulator(name='design', lattice='../soleil_lattice_2_pyaml/tests/SOLEIL_II_V3631_sym1_V001_database_rf.m', mat_key=None, linker=<pyaml.lattice.attribute_linker.PyAtAttributeElementsLinker object at 0x75e72782faa0>)

In [7]: sr.live
Out[7]: TangoControlSystem(name='live', tango_host='localhost:11000', debug_level=None, lazy_devices=True, scalar_aggregator='tango.pyaml.multi_attribute', vector_aggregator=None, timeout_ms=3000)

[gubaidulinvadim]

@JeanLucPons thanks for the fix. However, I find that the string representation is still incomplete. If I print the loaded SOLEIL II config, I get every component inside, which is hundreds of magnets. The string representation should probably stop before listing all individual elements.

sr
Accelerator(facility='Synchrotron SOLEIL', machine='sr', energy=2750000000.0, controls=[TangoControlSystem(name='live', tango_host='localhost:11000', debug_level=None, lazy_devices=True, scalar_aggregator='tango.pyaml.multi_attribute', vector_aggregator=None, timeout_ms=3000)], simulators=[Simulator(name='design', lattice='SOLEIL_II_V3631_sym1_V001_database_rf.m', mat_key=None, linker=<pyaml.lattice.attribute_linker.PyAtAttributeElementsLinker object at 0x7ad070904260>, description=None)], data_folder='/data/store', description=None, arrays=[<pyaml.arrays.bpm.BPM object at 0x7ad0702e7ad0>, <pyaml.arrays.element.Element object at 0x7ad0702e6ae0>, <pyaml.arrays.magnet.Magnet object at 0x7ad070b1be90>, <pyaml.arrays.magnet.Magnet object at 0x7ad0702984a0>, <pyaml.arrays.magnet.Magnet object at 0x7ad07029a180>, <pyaml.arrays.magnet.Magnet object at 0x7ad07029ae10>, <pyaml.arrays.magnet.Magnet object at 0x7ad07029b0e0>, <pyaml.arrays.magnet.Magnet object at 0x7ad07029bf80>, <pyaml.arrays.magnet.Magnet object at 0x7ad0702a4ad0>, <pyaml.arrays.magnet.Magnet object at 0x7ad070288b30>, <pyaml.arrays.magnet.Magnet object at 0x7ad070109250>, <pyaml.arrays.magnet.Magnet object at 0x7ad070117b00>, <pyaml.arrays.magnet.Magnet object at 0x7ad0701140b0>, <pyaml.arrays.magnet.Magnet object at 0x7ad0701144d0>, <pyaml.arrays.magnet.Magnet object at 0x7ad07280aff0>, <pyaml.arrays.magnet.Magnet object at 0x7ad070120800>, <pyaml.arrays.magnet.Magnet object at 0x7ad070120650>, <pyaml.arrays.magnet.Magnet object at 0x7ad0701203b0>, <pyaml.arrays.magnet.Magnet object at 0x7ad070121610>, <pyaml.arrays.magnet.Magnet object at 0x7ad070122ab0>, <pyaml.arrays.magnet.Magnet object at 0x7ad070140350>, <pyaml.arrays.magnet.Magnet object at 0x7ad070143590>, <pyaml.arrays.magnet.Magnet object at 0x7ad070142840>, <pyaml.arrays.magnet.Magnet object at 0x7ad070143710>, <pyaml.arrays.magnet.Magnet object at 0x7ad070143d40>, <pyaml.arrays.magnet.Magnet object at 0x7ad070142f90>, <pyaml.arrays.magnet.Magnet object at 0x7ad0701436e0>, <pyaml.arrays.magnet.Magnet object at 0x7ad07027fdd0>, <pyaml.arrays.magnet.Magnet object at 0x7ad07027f470>, <pyaml.arrays.magnet.Magnet object at 0x7ad0702e6f90>, <pyaml.arrays.magnet.Magnet object at 0x7ad0702e4110>, <pyaml.arrays.element.Element object at 0x