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 _rmsprop_update_numpy(self, var, g, mg, rms, mom, lr, decay, momentum,
                            centered):
    rms_t = rms * decay + (1 - decay) * g * g
    if centered:
      mg_t = mg * decay + (1 - decay) * g
      denom_t = rms_t - mg_t * mg_t
    else:
      mg_t = mg
      denom_t = rms_t
    mom_t = momentum * mom + lr * g / np.sqrt(denom_t, dtype=denom_t.dtype)
    var_t = var - mom_t
    return var_t, mg_t, rms_t, mom_t