class_docstr: Single excitation rotation with negative phase-shift outside the rotation subspace.
  
  .. math:: U_-(\phi) = \begin{bmatrix}
              e^{-i\phi/2} & 0 & 0 & 0 \\
              0 & \cos(\phi/2) & -\sin(\phi/2) & 0 \\
              0 & \sin(\phi/2) & \cos(\phi/2) & 0 \\
              0 & 0 & 0 & e^{-i\phi/2}
          \end{bmatrix}.
  
  **Details:**
  
  * Number of wires: 2
  * Number of parameters: 1
  * Number of dimensions per parameter: (0,)
  * Gradient recipe: :math:`\frac{d}{d\phi}f(U_-(\phi)) = \frac{1}{2}\left[f(U_-(\phi+\pi/2)) - f(U_-(\phi-\pi/2))\right]`
    where :math:`f` is an expectation value depending on :math:`U_-(\phi)`.
  
  Args:
      phi (float): rotation angle :math:`\phi`
      wires (Sequence[int] or int): the wires the operation acts on
      id (str or None): String representing the operation (optional)
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code: def __init__(self, phi, wires, id=None):
      super().__init__(phi, wires=wires, id=id)
  
imports: import functools
  import numpy
  from scipy.sparse import csr_matrix
  import pennylane
  from pennylane.operation import Operation
label_desc: Use image node_id 2 to create a new SingleExcitationMinus object from inherited base classes: Operation with example: obj = SingleExcitationMinus(phi, wires, id)