new_contents: """ PyShrunk - Rutgers University URL Shortener
  
  Implements database-level interactions for the shrunk application.
  """
  
  class ShrunkClient(object):
      """A class for database interactions."""
  
      def __init__(self, host=None, port=None):
          """
          Create a new client connection.
  
          :Parameters:
            - `host` (optional): the hostname to connect to; defaults to
              "localhost"
            - `port` (optional): the port to connect to on the server; defaults to
              the database default if not present
          """
          pass
  
      def create_short_url(self, long_url, netid=None):
          """Given a long URL, create a new short URL.
          
          Randomly creates a new short URL and updates the Shrunk database.
  
          :Parameters:
            - `long_url`: The original URL to shrink.
            - `netid` (optional): The creator of this URL.
  
          :Returns:
            The shortened URL, or None if an error occurs.
          """
          pass
  
      def delete_url(self, short_url):
          """Given a short URL, delete it from the database.
  
          This deletes all information associated with the short URL and wipes all
          appropriate databases.
          
          :Parameters:
            - `short_url`: The shortened URL to dete.
  
          :Returns:
            A response in JSON detailing the effect of the database operations.
          """
          pass
  
      def delete_user_urls(self, netid):
          """Deletes all URLs associated with a given NetID.
  
          The response, encoded as a JSON-compatible Python dict, will at least
          contained an "nRemoved" indicating the number of records removed.
  
          :Parameters:
            - `netid`: The NetID of the URLs to delete.
          
          :Returns:
            A response in JSON detailing the effect of the database operations.
          """
          pass
  
      def get_url_info(self, short_url):
          """Given a short URL, return information about it.
  
          This returns a dictionary containing the following fields:
            - url : The original unshrunk URL
            - timeCreated: The time the URL was created, expressed as an ISODate
              instance
            - netid : If it exists, the creator of the shortened URL
            - visits : The number of visits to this URL
  
          :Parameters:
            - `short_url`: A shortened URL.
          """
          pass
  
      def get_long_url(self, short_url):
          """Given a short URL, returns the long URL."""
          pass
  
      def get_visits(self, short_url):
          """Returns all visit information to the given short URL."""
          pass
  
      def get_num_visits(self, short_url):
          """Given a short URL, return the number of visits.
          
          :Parameters:
            A shortened URL obtained from Shrunk.
  
          :Returns:
            A nonnegative integer indicating the number of times the URL has been
            visited, or None if the URL does not exist in the database.
          """
          pass
  
      def get_urls(self, netid):
          """Gets all the URLs created by the given NetID.
          
          The return value is a JSON-like Python dictionary.
          """
          pass
  
      def visit(self, short_url, source_ip):
          """Visits the given URL and logs visit information.
          
          On visiting a URL, this is guaranteed to perform at least the following
          side effects if the URL is valid:
            - Increment the hit counter
            - Log the visitor
  
          If the URL is invalid, no side effects will occur.
  
          :Returns:
            The long URL corresponding to the short URL, or None if no such URL
            was found in the database.
          """
          pass
  
      @staticmethod
      def _aggregate(collection, query):
          """Performs an aggregation on the database.
  
          This performs an aggregation on the database. This ensures that errors
          and failed queries are handled in a uniform fashion.
          """
          pass
  
      @staticmethod
      def _generate_unique_key():
          """Generates a unique key in the database."""
          pass
  
subject: Add shrunk_client.py skeleton