使用BaseBuiltin类来自定义函数，判断两个普通字段内容是否有重叠

可以使用BaseBuiltin类来自定义函数，以下是判断两个普通字段内容是否有重叠的示例代码：

from jinja2.ext import Extension, nodes
from jinja2 import TemplateSyntaxError

class OverlapCheckExtension(Extension):
    tags = {'overlap_check'}

    def parse(self, parser):
        lineno = next(parser.stream).lineno

        # Parse the two variables to check for overlap
        var1 = parser.parse_expression()
        var2 = parser.parse_expression()

        # Make sure there are no extra arguments
        if parser.stream.current.type != 'block_end':
            raise TemplateSyntaxError('Unexpected arguments to overlap_check', lineno)

        return nodes.CallBlock(self.call_method('overlap_check', [var1, var2]), [], [], []).set_lineno(lineno)

    def overlap_check(self, var1, var2, caller):
        # Check if the two variables overlap
        if set(var1) & set(var2):
            return caller()
        else:
            return ''

在模板中使用该自定义函数：

{% overlap_check field1 field2 %}
    <p>There is an overlap between field1 and field2</p>
{% endoverlap_check %}

其中`field1`和`field2`是需要比较的两个普通字段。如果它们有重叠，就会输出`<p>There is an overlap between field1 and field2</p>`。否则，什么也不会输出。