I need assistance in implementing this function correctly please.

def get$\_$weather$\_$report$($takeoff$,$weather$)$:

$"""$

Returns the most recent weather report at or before take$-$off.

The weather is a dictionary whose keys are ISO formatted timestamps and whose values

are weather reports. For example, here is an example of a $($small portion of$)$ a

weather dictionary:

$\{$

$"2017-04-21$T$08$:$00$:$00-04$:$00"$: $\{$

"visibility": $\{$

"prevailing": $10\mathrm{.}0,$

"units": $"$SM$"$

$\},$

"wind": $\{$

"speed": $13\mathrm{.}0,$

"crosswind": $2\mathrm{.}0,$

"units": $"$KT$"$

$\},$

"temperature": $\{$

"value": $13\mathrm{.}9,$

"units": $"$C$"$

$\},$

$"$sky$"$: $[$

$\{$

"cover": "clouds",

"type": "broken",

"height": $700\mathrm{.}0,$

"units": $"$FT$"$

$\}$

$],$

"code": $"201704211056$Z$"$

$\},$

$"2017-04-21$T$07$:$00$:$00-04$:$00"$: $\{$

"visibility": $\{$

"prevailing": $10\mathrm{.}0,$

"units": $"$SM$"$

$\},$

"wind": $\{$

"speed": $13\mathrm{.}0,$

"crosswind": $2\mathrm{.}0,$

"units": $"$KT$"$

$\},$

"temperature": $\{$

"value": $13\mathrm{.}9,$

"units": $"$C$"$

$\},$

$"$sky$"$: $[$

$\{$

"type": "overcast",

"height": $700\mathrm{.}0,$

"units": $"$FT$"$

$\}$

$],$

"code": $"201704210956$Z$"$

$\}$

$...$

$\},$

If there is a report whose timestamp matches the ISO representation of takeoff,

this function uses that report. Otherwise it searches the dictionary for the most

recent report before $($but not equal to$)$ takeoff. If there is no such report, it

returns None.

Example: If takeoff was as $8$ am on April $21,2017($Eastern$),$ this function returns

the value for key $\text{'}2017-04-21$T$08$:$00$:$00-04$:$00\text{'}.$ If there is no additional report at

$9$ am$,$ a $9$ am takeoff would use this value as well.

Parameter takeoff: The takeoff time

Precondition: takeoff is a datetime object

Paramater weather: The weather report dictionary

Precondition: weather is a dictionary formatted as described above

$"""$

# HINT: Looping through the dictionary is VERY slow because it is so large

# You should convert the takeoff time to an ISO string and search for that first.

# Only loop through the dictionary as a back$-$up if that fails.

# Search for time in dictionary

# As fall back, find the closest time before takeoff