[Selectors]
● matchLabels
It consists of key, and value pairs where the values are matched using equality-based requirements that allow filtering by label keys and values.
Valid operators include =, ==, !=.
● matchExpressions
A list of requirements made by specifying key, list of values, and operator that relates the key and values.
It consists of a key, operator, and values Set-based label requirements allow filtering keys according to a set of values.
Valid operators include In, NotIn, Exists, and DoesNotExist.

# EXAMPLE 1 :-
apiVersion: v1
kind: ReplicationController
metadata:
  name: REPLICATIONCONTROLLER_NAME
spec:
  replicas: NO
  selector:
    KEY: VALUE
    KEY: VALUE
........
........
........

# EXAMPLE 2 :-
apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: REPLICASET_NAME
spec:
  replicas: NO
  selector:
    matchLabels:                                                # This option was added
      KEY: VALUE
      KEY: VALUE
........
........
........

# EXAMPLE 3 :-
apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: REPLICASET_NAME
spec:
  replicas: NO
  selector:
    matchExpressions:
      - {key: KEY_NAME, operator: In, values: [VALUE_NAME, VALUE_NAME]}
      - {key: KEY_NAME, operator: NotIn, values: [VALUE_NAME]}
      - {key: KEY_NAME, operator: NotIn, values: [VALUE_NAME, VALUE_NAME]}
........
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........

# EXAMPLE 4 :-
........
........
........
spec:
  selector:
    matchExpressions:
    - key: KEY_NAME
      operator: In
      values: ["VALUE_NAME", "VALUE_NAME"]
........
........
........

# EXAMPLE 5 :-
........
........
........
spec:
  selector:
    matchLabels:
      KEY: VALUE
    matchExpressions:
      - {key: KEY_NAME, operator: NotIn, values: [VALUE_NAME]}
........
........
........
