Searches for the map for a given key.
Searches for the map for a given key.
the key to search for
true if the key is in the map, false otherwise
      
    
      
      
    
      Queries the value for a given key.
Queries the value for a given key.
the key to look for
the value if it was found at the key, otherwise None
      
    
      
      
    
      
      
    
      
      
    
      
      
    
      
      
    
      
      
    
      Inserts a new entry into the map.
Inserts a new entry into the map.
the key to insert
the value to store for the given key
the previous value stored at the key, or None if the key was not in the map
      
    
      Removes an entry from the map.
Removes an entry from the map.
the key to remove
the removed value which had been stored at the key, or None if the key was not in the map
      
    
      Reports the number of entries in the map.
Reports the number of entries in the map. This operation may take up to O(n) time, depending on the implementation.