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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 create_key(policy=None, description=None, key_usage=None, region=None,
               key=None, keyid=None, profile=None):
    '''
    Creates a master key.

    CLI example::

        salt myminion boto_kms.create_key '{"Statement":...}' "My master key"
    '''
    conn = _get_conn(region=region, key=key, keyid=keyid, profile=profile)

    r = {}
    _policy = salt.serializers.json.serialize(policy)
    try:
        key_metadata = conn.create_key(
            _policy,
            description=description,
            key_usage=key_usage
        )
        r['key_metadata'] = key_metadata['KeyMetadata']
    except boto.exception.BotoServerError as e:
        r['error'] = __utils__['boto.get_error'](e)
    return r