def coerce(cls, string):
        """Create a :class:`Requirement` object from a given package spec."""
        match = re.match(cls.spec_regex, string)
        if not match:
            raise InvalidRequirementSpecError("could not parse requirement")
        package = match.group(1)
        if all(match.group(2, 3)):
            version = "".join(match.group(2, 3))
        else:
            version = None
        return cls(package, version)
def call_vision_api(image_filename, api_keys):
    api_key = api_keys['microsoft']
    post_url = "https://api.projectoxford.ai/vision/v1.0/analyze?visualFeatures=Categories,Tags,Description,Faces,ImageType,Color,Adult&subscription-key=" + api_key

    image_data = open(image_filename, 'rb').read()
    result = requests.post(post_url, data=image_data, headers={'Content-Type': 'application/octet-stream'})
    result.raise_for_status()

    return result.text