class_docstr: An expression used to select node by node's labels
  Attributes:
      key: the key of label
      operator: In、NotIn、Exists、DoesNotExist
class_docstr_tok: ["An","expression","used","to","select","node","by","node","'s","labels","Attributes",":","key",":","the","key","of","label","operator",":","In\u3001NotIn\u3001Exists\u3001DoesNotExist"]
code: def __init__(
      self, key: str, operator: Union[In, NotIn, Exists, DoesNotExist]
  ):
      self.key = key
      self.operator = operator
  
imports: from typing import Dict, Union, Optional, TYPE_CHECKING
  from ray.util.annotations import PublicAPI
label_desc: Use image node_id 1 to create a new _LabelMatchExpression object  with example: obj = _LabelMatchExpression(key, operator)