def integers(sequence_of_sequences):
    """
    Returns a new list that contains all the integers
    in the subsequences of the given sequence, in the order that they
    appear in the subsequences.
    For example, if the argument is:
        [(3, 1, 4),
         (10, 'hi', 10),
         [1, 2.5, 3, 4],
         'hello',
         [],
         ['oops'],
         [[55], [44]],
         [30, -4]
        ]
    then this function returns:
        [3, 1, 4, 10, 10, 1, 3, 4, 30, -4]

    Type hints:
      :type sequence_of_sequences: (list|tuple) of (list|tuple|string)
      :rtype: list of int
    """
    # -------------------------------------------------------------------------
    # DONE: 3. Implement and test this function.
    #   Note that you should write its TEST function first (above).
    # -------------------------------------------------------------------------
    ###########################################################################
    # HINT: The
    #           type
    #       function can be used to determine the type of
    #       its argument (and hence to see if it is an integer).
    #       For example, you can write expressions like:
    #         -- if type(34) is int: ...
    #         -- if type(4.6) is float: ...
    #         -- if type('three') is str: ...
    #         -- if type([1, 2, 3]) is list: ...
    #       Note that the returned values do NOT have quotes.
    #       Also, the   is   operator tests for equality (like ==)
    #       but is more appropriate than == in this situation.
    # -------------------------------------------------------------------------
    ###########################################################################
    # -------------------------------------------------------------------------
    # DIFFICULTY AND TIME RATINGS (see top of this file for explanation)
    #    DIFFICULTY:      6
    #    TIME ESTIMATE:  10 minutes.
    # -------------------------------------------------------------------------
    s = []
    for k in range(len(sequence_of_sequences)):
        for j in range(len(sequence_of_sequences[k])):
            if type(sequence_of_sequences[k][j]) == int:
                s = s + [sequence_of_sequences[k][j]]
    return s