docs: def is_package(name):
      """Check if string maps to a package installed via pip.
  
      name (unicode): Name of package.
      RETURNS (bool): True if installed package, False if not.
      """
      name = name.lower()  # compare package name against lowercase name
      packages = pkg_resources.working_set.by_key.keys()
      for package in packages:
          if package.lower().replace('-', '_') == name:
              return True
      return False