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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 get_include():
    '''return a list of include directories.'''
    dirname = os.path.abspath(os.path.join(os.path.dirname(__file__)))

    #
    # Header files may be stored in different relative locations
    # depending on installation mode (e.g., `python setup.py install`,
    # `python setup.py develop`. The first entry in each list is
    # where develop-mode headers can be found.
    #
    htslib_possibilities = [os.path.join(dirname, '..', 'htslib'),
                            os.path.join(dirname, 'include', 'htslib')]
    samtool_possibilities = [os.path.join(dirname, '..', 'samtools'),
                             os.path.join(dirname, 'include', 'samtools')]

    includes = [dirname]
    for header_locations in [htslib_possibilities, samtool_possibilities]:
        for header_location in header_locations:
            if os.path.exists(header_location):
                includes.append(os.path.abspath(header_location))
                break

    return includes