Intelligently sets the initial value of autoescaping based on the
    filename of the template.  This is the recommended way to configure
    autoescaping if you do not want to write a custom function yourself.

    If you want to enable it for all templates created from strings or
    for all templates with `.html` and `.xml` extensions::

        from jinja2 import Environment, select_autoescape
        env = Environment(autoescape=select_autoescape(
            enabled_extensions=('html', 'xml'),
            default_for_string=True,
        ))

    Example configuration to turn it on at all times except if the template
    ends with `.txt`::

        from jinja2 import Environment, select_autoescape
        env = Environment(autoescape=select_autoescape(
            disabled_extensions=('txt',),
            default_for_string=True,
            default=True,
        ))

    The `enabled_extensions` is an iterable of all the extensions that
    autoescaping should be enabled for.  Likewise `disabled_extensions` is
    a list of all templates it should be disabled for.  If a template is
    loaded from a string then the default from `default_for_string` is used.
    If nothing matches then the initial value of autoescaping is set to the
    value of `default`.

    For security reasons this function operates case insensitive.

    .. versionadded:: 2.9

def select_autoescape(enabled_extensions=('html', 'htm', 'xml'),
                      disabled_extensions=(),
                      default_for_string=True,
                      default=False):
    """Intelligently sets the initial value of autoescaping based on the
    filename of the template.  This is the recommended way to configure
    autoescaping if you do not want to write a custom function yourself.

    If you want to enable it for all templates created from strings or
    for all templates with `.html` and `.xml` extensions::

        from jinja2 import Environment, select_autoescape
        env = Environment(autoescape=select_autoescape(
            enabled_extensions=('html', 'xml'),
            default_for_string=True,
        ))

    Example configuration to turn it on at all times except if the template
    ends with `.txt`::

        from jinja2 import Environment, select_autoescape
        env = Environment(autoescape=select_autoescape(
            disabled_extensions=('txt',),
            default_for_string=True,
            default=True,
        ))

    The `enabled_extensions` is an iterable of all the extensions that
    autoescaping should be enabled for.  Likewise `disabled_extensions` is
    a list of all templates it should be disabled for.  If a template is
    loaded from a string then the default from `default_for_string` is used.
    If nothing matches then the initial value of autoescaping is set to the
    value of `default`.

    For security reasons this function operates case insensitive.

    .. versionadded:: 2.9
    """
    enabled_patterns = tuple('.' + x.lstrip('.').lower()
                             for x in enabled_extensions)
    disabled_patterns = tuple('.' + x.lstrip('.').lower()
                              for x in disabled_extensions)
    def autoescape(template_name):
        if template_name is None:
            return default_for_string
        template_name = template_name.lower()
        if template_name.endswith(enabled_patterns):
            return True
        if template_name.endswith(disabled_patterns):
            return False
        return default
    return autoescape