将值显示为文本，仅显示altair中具有最大高度的条形图

import altair as alt
from vega_datasets import data

source = data.barley()

chart = alt.Chart(source).mark_bar().encode(
    x='site',
    y='count()'
)

max_height = source['count'].max()
filtered_chart = chart.transform_filter(
    alt.datum['count'] == max_height
)

text_chart = filtered_chart.mark_text(
    align='center',
    baseline='bottom',
    dy=-5,  # 调整文本位置
    fontSize=11,
).encode(
    text='count()'
)

final_chart = filtered_chart + text_chart