code: def commutator(expr1, expr2):
      
      expr1 = expr1.to_expr().simplify()
      expr2 = expr2.to_expr().simplify()
      return (expr1 * expr2 - expr2 * expr1).simplify()
docs: Returns [expr1, expr2] = expr1 * expr2 - expr2 * expr1.
  
      Args:
          expr1 (Expr, Term or Pauli operator): Pauli's expression.
          expr2 (Expr, Term or Pauli operator): Pauli's expression.
  
      Returns:
          Expr: expr1 * expr2 - expr2 * expr1.