def _maybe_fill ( arr , fill_value = np . nan ) : if _isna_compat ( arr , fill_value ) : arr . fill ( fill_value ) return arr
python fillna inplace not working
if we have a compatible fill_value and arr dtype then fill
def _maybe_fill(arr, fill_value=np.nan):
    """
    if we have a compatible fill_value and arr dtype, then fill
    """
    if _isna_compat(arr, fill_value):
        arr.fill(fill_value)
    return arr