def load(self, filename, create_if_missing=True):
        filename = Path(filename)
        if not filename.exists() and create_if_missing:
            self.load_pip_requirements()
            with filename.open("w") as f:
                f.write(yaml.dump(self.serialized, default_flow_style=False,
                                  encoding=None))
            self.filename = filename
            return self.save(filename)
        with filename.open() as f:
            for group, requirements in yaml.load(f.read()).items():
                for requirement in requirements:
                    self[group].add(Requirement.coerce(requirement))
        self.filename = filename
def i1beta_phasor(up, i1, beta, r1, xd, xq, ax=0):
    """creates a phasor plot
    up: internal voltage
    i1: current
    beta: angle i1 vs up [deg]
    r1: resistance
    xd: reactance in direct axis
    xq: reactance in quadrature axis"""

    i1d, i1q = (i1*np.sin(beta/180*np.pi), i1*np.cos(beta/180*np.pi))
    uxdq = ((r1*i1d - xq*i1q), (r1*i1q + xd*i1d))
    __phasor_plot(ax, up, (i1d, i1q), uxdq)