code: def __init__(self, definition: VariableDefinition):
      if definition.get("has missing", False):
          self.has_missing = True
          try:
              exists_pred = predicates.ExistsPredicate(
                  definition["field"]
              )
              self.predicates.append(exists_pred)
          except KeyError:
              pass
      else:
          self.has_missing = False
  
imports: from __future__ import annotations
  from typing import TYPE_CHECKING
  from dedupe import predicates
label_desc: Use image node_id 5 to create a new Variable object from inherited base classes: object with example: obj = Variable(definition)