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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 pem_finger(path=None, key=None, sum_type='sha256'):
    '''
    Pass in either a raw pem string, or the path on disk to the location of a
    pem file, and the type of cryptographic hash to use. The default is SHA256.
    The fingerprint of the pem will be returned.

    If neither a key nor a path are passed in, a blank string will be returned.
    '''
    if not key:
        if not os.path.isfile(path):
            return ''

        with salt.utils.files.fopen(path, 'rb') as fp_:
            key = b''.join([x for x in fp_.readlines() if x.strip()][1:-1])

    pre = getattr(hashlib, sum_type)(key).hexdigest()
    finger = ''
    for ind, _ in enumerate(pre):
        if ind % 2:
            # Is odd
            finger += '{0}:'.format(pre[ind])
        else:
            finger += pre[ind]
    return finger.rstrip(':')