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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def port(alias_name, default=None, allow_none=False):
 """Get the port from the docker link alias or return the default. Args: alias_name: The docker link alias default: The default value if the link isn't available allow_none: If the return value can be `None` (i.e. optional) Examples: Assuming a Docker link was created with ``docker --link postgres:db`` and the resulting environment variable is ``DB_PORT=tcp://172.17.0.82:5432``. 5432 """

    warnings.warn('Will be removed in v1.0', DeprecationWarning, stacklevel=2)
    try:
        return int(_split_docker_link(alias_name)[2])
    except KeyError as err:
        if default or allow_none:
            return default
        else:
            raise err