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 __init__(self, cost_withGradients):
        super(CostModel, self).__init__()

        self.cost_type = cost_withGradients

        # --- Set-up evaluation cost
        if self.cost_type is None:
            self.cost_withGradients = constant_cost_withGradients
            self.cost_type = 'Constant cost'

        elif self.cost_type == 'evaluation_time':
            self.cost_model = GPModel()
            self.cost_withGradients = self._cost_gp_withGradients
            self.num_updates = 0
        else:
            self.cost_withGradients = cost_withGradients
            self.cost_type = 'User defined cost'