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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 make_image(location, size, fmt):
    '''
    Create a blank virtual machine image file of the specified size in
    megabytes. The image can be created in any format supported by qemu

    CLI Example:

    .. code-block:: bash

        salt '*' qemu_img.make_image /tmp/image.qcow 2048 qcow2
        salt '*' qemu_img.make_image /tmp/image.raw 10240 raw
    '''
    if not os.path.isabs(location):
        return ''
    if not os.path.isdir(os.path.dirname(location)):
        return ''
    if not __salt__['cmd.retcode'](
            'qemu-img create -f {0} {1} {2}M'.format(
                fmt,
                location,
                size),
                python_shell=False):
        return location
    return ''