editing docs

pennylane/fermi/fermionic.py

@@ -326,6 +326,7 @@ def to_mat(self, n_orbitals=None, format="dense", buffer_size=None):
 
  def shift_operator(self, initial_position, final_position):
  r"""Shifts an operator in the FermiWord from ``initial_position`` to ``final_position`` by applying the fermionic anti-commutation relations.
+
  There are three `anti-commutator relations <https://en.wikipedia.org/wiki/Creation_and_annihilation_operators#Creation_and_annihilation_operators_in_quantum_field_theories>`_:
 
  .. math::
@@ -351,8 +352,8 @@ def shift_operator(self, initial_position, final_position):
 
  Raises:
  TypeError: if ``initial_position`` or ``final_position`` is not an integer
- ValueError: if ``initial_position`` or ``final_position`` are outside the range ``[0, len(self) - 1]``
- where ``len(self)`` is the number of operators in the FermiWord.
+ ValueError: if ``initial_position`` or ``final_position`` are outside the range ``[0, len(fermiword) - 1]``
+ where ``len(fermiword)`` is the number of operators in the FermiWord.
 
 
  **Example**