Return a sequence of characters corresponding to the specified base.

    Example::

        >>> calculate_base_sequence([ ('0', '9'), ('A', 'F') ])
        '0123456789ABCDEF'

    @param base_offsets: a list of character offsets in the form of tuples
           ``(x, y)`` where ``x`` corresponds to the first character of a
           sequence and ``y`` to the last character of this sequence.

    @return a sequence of characters, i.e., a string, corresponding to the
            specified base.

def calculate_base_sequence(base_offsets):
    """
    Return a sequence of characters corresponding to the specified base.

    Example::

        >>> calculate_base_sequence([ ('0', '9'), ('A', 'F') ])
        '0123456789ABCDEF'

    @param base_offsets: a list of character offsets in the form of tuples
           ``(x, y)`` where ``x`` corresponds to the first character of a
           sequence and ``y`` to the last character of this sequence.

    @return a sequence of characters, i.e., a string, corresponding to the
            specified base.
    """
    return ''.join([ chr(c) for c in list(itertools.chain.from_iterable(
                      [ range(ord(x), ord(y) + 1) for (x, y) in base_offsets ])) ])