code: def install_requirements(self, path, index=None):
          
          cmd = 'install -r {0}'.format(path)
          if index:
  
              cmd = 'install --index-url {0} -r {1}'.format(index, path)
  
          self.pip(cmd)
docs: Install packages from a requirements.txt file.
  
          Args:
              path (str): The path to the requirements file.
              index (str): The URL for a pypi index to use.