[Python] Interpolate among Groups in pandas DataFrame

I'm looking for the most efficient way to interpolate across Groups in pandas DataFrame for a big data volume. For example I have some groups that have all the values, and some that have none. In the example below data is groupby('Group'), Groups A and D have all the values at all Time, and Groups B,C and E have none.

How to find the most efficient way to interpolate Group E based on Group D specifically, giving the logic that Group D is the nearest and thus to be used for interpolation.

I am new to python.

Group Time Value
A 1 10
A 2 15
A 3 30
A 4 50
B 1 NaN
B 2 NaN
B 3 NaN
B 4 NaN
C 1 NaN
C 2 NaN
C 3 NaN
C 4 NaN
D 1 5
D 2 10
D 3 15
D 4 20
E 1 NaN
E 2 NaN
E 3 NaN
E 4 NaN


The expected output is something like the below

Group Time Value
A 1 10
A 2 15
A 3 30
A 4 50
B 1 10
B 2 15
B 3 30
B 4 50
C 1 5
C 2 10
C 3 15
C 4 20
D 1 5
D 2 10
D 3 15
D 4 20
E 1 5
E 2 10
E 3 15
E 4 20

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