class_docstr: Base class for min-heaps.
  
  A MinHeap stores a collection of key-value pairs ordered by their values.
  It supports querying the minimum pair, inserting a new pair, decreasing the
  value in an existing pair and deleting the minimum pair.
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docstr: Returns whether a key exists in the heap.
  
  Parameters
  ----------
  key : any hashable object.
      The key to be looked up.
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code: def __contains__(self, key):
      """Returns whether a key exists in the heap.
  
      Parameters
      ----------
      key : any hashable object.
          The key to be looked up.
      """
      return key in self._dict
  
imports: from heapq import heappop, heappush
  from itertools import count
  import networkx
label_desc: Use image node_id 9 for calling the MinHeap obj's underlying member method code with example usage: obj.__contains__(key) and returns: unknown