def install_pip(self, package, save=True, save_dev=False):
        """Installs a pip package.

        :param save: if `True`, pins the package to the Hydrogen requirements
            YAML file.
        :param save_dev: if `True`, pins the package as a development
            dependency to the Hydrogen requirements YAML file.
        :param return: a **single** :class:`Requirement` object, representing
            the installed version of the given package.
        """
        requirement = Requirement.coerce(package)
        click.echo("pip install " + requirement.package)
        cmd = envoy.run("pip install {}".format(str(requirement)))
        if cmd.status_code == 0:
            installed_packages = get_installed_pypackages()
            package = installed_packages[requirement.package]
            requirement.version = "=={}".format(package.version)
            if save:
                self.requirements["all"].add(requirement)
            if save_dev:
                self.requirements["dev"].add(requirement)
            if save or save_dev:
                self.requirements.save()
            return requirement
        else:
            fatal(cmd.std_err)
def winding_factors(wdg, n=8, ax=0):
    """plot winding factors"""
    ax = plt.gca()
    ax.set_title(f'Winding factors Q={wdg.Q}, p={wdg.p}, q={round(wdg.q,4)}')
    ax.grid(True)
    order, kwp, kwd, kw = np.array([(n, k1, k2, k3)
                                    for n, k1, k2, k3 in zip(wdg.kw_order(n),
                                                             wdg.kwp(n),
                                                             wdg.kwd(n),
                                                             wdg.kw(n))]).T
    try:
        markerline1, stemlines1, _ = ax.stem(order-1, kwp, 'C1:', basefmt=" ",
                                             markerfmt='C1.',
                                             use_line_collection=True, label='Pitch')
        markerline2, stemlines2, _ = ax.stem(order+1, kwd, 'C2:', basefmt=" ",
                                             markerfmt='C2.',
                                             use_line_collection=True, label='Distribution')
        markerline3, stemlines3, _ = ax.stem(order, kw, 'C0-', basefmt=" ",
                                             markerfmt='C0o',
                                             use_line_collection=True, label='Total')
        ax.set_xticks(order)
        ax.legend()
    except ValueError:  # empty sequence
        pass