Summing values in line chart

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Hello,
i am trying to build a line chart with date(Month_Year) in X axis and 2 lines (one for radiology and second for lab ) … i am trying to sum up the values of the lab for each month … same for radiology … but i don’t know how to sum up values in line chart.

i am using the below code:

dff4=dff1[[‘date’,'Radiology ','Lab_charges ']]
dff4=dff4.set_index(‘date’)
st.line_chart(dff4)

i appreciate help.