class_docstr: FermiA(orbital)
  The fermionic annihilation operator :math:`a`
  
  For instance, the operator ``qml.FermiA(2)`` denotes :math:`a_2`. This operator applied
  to :math:`\ket{0010}` gives :math:`\ket{0000}`.
  
  Args:
      orbital(int): the non-negative integer indicating the orbital the operator acts on.
  
  .. note:: While the ``FermiA`` class represents a mathematical operator, it is not a PennyLane qubit :class:`~.Operator`.
  
  .. seealso:: :class:`~pennylane.FermiC`
  
  **Example**
  
  To construct the operator :math:`a_0`:
  
  >>> FermiA(0)
  a(0)
  
  This can be combined with the creation operator :class:`~pennylane.FermiC`. For example,
  :math:`a^{\dagger}_0 a_1 a^{\dagger}_2 a_3` can be constructed as:
  
  >>> qml.FermiC(0) * qml.FermiA(1) * qml.FermiC(2) * qml.FermiA(3)
  a⁺(0) a(1) a⁺(2) a(3)
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code: def __init__(self, orbital):
      if not isinstance(orbital, int) or orbital < 0:
          raise ValueError(
              f"FermiA: expected a single, positive integer value for orbital, but received {orbital}"
          )
      operator = {(0, orbital): "-"}
      super().__init__(operator)
  
imports: import re
  from copy import copy
  from numbers import Number
  from numpy import ndarray
  import pennylane
label_desc: Use image node_id 1 to create a new FermiA object from inherited base classes: FermiWord with example: obj = FermiA(orbital)