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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 mkdir(dir_path,
          user=None,
          group=None,
          mode=None):
    '''
    Ensure that a directory is available.

    CLI Example:

    .. code-block:: bash

        salt '*' file.mkdir /opt/jetty/context
    '''
    dir_path = os.path.expanduser(dir_path)

    directory = os.path.normpath(dir_path)

    if not os.path.isdir(directory):
        # If a caller such as managed() is invoked  with makedirs=True, make
        # sure that any created dirs are created with the same user and group
        # to follow the principal of least surprise method.
        makedirs_perms(directory, user, group, mode)

    return True