code: def auto_install(self):
          
          value = self.get(property_name='auto_install',
                           environment_variable='PIP_ACCEL_AUTO_INSTALL',
                           configuration_option='auto-install')
          if value is not None:
              return coerce_boolean(value)
docs: Whether automatic installation of missing system packages is enabled.
  
          :data:`True` if automatic installation of missing system packages is
          enabled, :data:`False` if it is disabled, :data:`None` otherwise (in this case
          the user will be prompted at the appropriate time).
  
          - Environment variable: ``$PIP_ACCEL_AUTO_INSTALL`` (refer to
            :func:`~humanfriendly.coerce_boolean()` for details on how the
            value of the environment variable is interpreted)
          - Configuration option: ``auto-install`` (also parsed using
            :func:`~humanfriendly.coerce_boolean()`)
          - Default: :data:`None`