```common lisp
(cl:in-package #:cleavir-dataflow-analysis)

(defclass port ()
  ((%operation :initarg :operation :reader operation)
   (%datum :initarg :datum :reader datum)))

(defclass input (port)
  ((%outputs :initform '() :initarg outputs :accessor outputs)))

(defclass output (port)
  ((%inputs :initform '() :initarg inputs :accessor inputs)))

(defclass operation ()
  ((%instruction :initarg :instruction :reader instruction)
   (%inputs :initform '() :initarg inputs :accessor inputs)
   (%outputs :initform '() :initarg outputs :accessor outputs)))

(defclass dataflow ()
  (;; This hash table maps each instruction to its corresponding
   ;; operation
   (%operations :initform (make-hash-table :test #'eq)
		:initarg :operations
		:accessor operations)))

(defun dataflow-analysis (initial-instruction)
  (let ((result (make-instance 'dataflow)))
    (cleavir-ir:map-instructions-arbitrary-order
     (lambda (instruction)
       (setf (gethash instruction (operations result))
	     (make-instance 'operation
	       :instruction instruction)))
     initial-instruction)
    result))
```

Add comment explaining the purpose of the slot OPERATION in class PORT.
user
```common lisp
(cl:in-package #:cleavir-dataflow-analysis)

(defclass port ()
  (;; The operation to which this port belongs.
   (%operation :initarg :operation :reader operation)
   (%datum :initarg :datum :reader datum)))

(defclass input (port)
  ((%outputs :initform '() :initarg outputs :accessor outputs)))

(defclass output (port)
  ((%inputs :initform '() :initarg inputs :accessor inputs)))

(defclass operation ()
  ((%instruction :initarg :instruction :reader instruction)
   (%inputs :initform '() :initarg inputs :accessor inputs)
   (%outputs :initform '() :initarg outputs :accessor outputs)))

(defclass dataflow ()
  (;; This hash table maps each instruction to its corresponding
   ;; operation
   (%operations :initform (make-hash-table :test #'eq)
		:initarg :operations
		:accessor operations)))

(defun dataflow-analysis (initial-instruction)
  (let ((result (make-instance 'dataflow)))
    (cleavir-ir:map-instructions-arbitrary-order
     (lambda (instruction)
       (setf (gethash instruction (operations result))
	     (make-instance 'operation
	       :instruction instruction)))
     initial-instruction)
    result))
```
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