Fill NA/NaN values using the specified method.
If a scalar value is passed it is used to fill all missing values.
Alternatively, an array-like ‘value’ can be given. It’s expected
that the array-like have the same length as ‘self’.
Method to use for filling holes in reindexed Series
pad / ffill: propagate last valid observation forward to next valid
backfill / bfill: use NEXT valid observation to fill gap.
If method is specified, this is the maximum number of consecutive
NaN values to forward/backward fill. In other words, if there is
a gap with more than this number of consecutive NaNs, it will only
be partially filled. If method is not specified, this is the
maximum number of entries along the entire axis where NaNs will be
With NA/NaN filled.