I keep getting the following error from the below functions: The call str$\_$to$\_$time$(\text{'}2016-04-15\text{'},$ None$)$ returns None, not datetime.datetime$(2016,4,15,0,0).$

import pytz

from dateutil import parser

def str$\_$to$\_$time$($timestamp$,$tzsource$=$None$)$:

$"""$

Returns the datetime object for the given timestamp $($or None if timestamp is

invalid$).$

This function should just use the parse function in dateutil.parser to

convert the timestamp to a datetime object. If it is not a valid date $($so

the parser crashes$),$ this function should return None.

If the timestamp has a time zone, then it should keep that time zone even if

the value for tzsource is not None. Otherwise, if timestamp has no time zone

and tzsource is not None, then this function will use tzsource to assign

a time zone to the new datetime object.

The value for tzsource can be None, a string, or a datetime object. If it

is a string, it will be the name of a time zone, and it should localize the

timestamp. If it is another datetime, then the datetime object created from

timestamp should get the same time zone as tzsource.

Parameter timestamp: The time stamp to convert

Precondition: timestamp is a string

Parameter tzsource: The time zone to use $($OPTIONAL$)$

Precondition: tzsource is either None, a string naming a valid time zone,

or a datetime object.

$"""$

# HINT: Use the code from the previous exercise and add time zone handling.

# Use localize if tzsource is a string; otherwise replace the time zone if not None

try:

time $=$ parser.parse$($timestamp$)$

except ValueError:

return None

if time.tzinfo is not None:

return time

if tzsource is None:

return None

if isinstance$($tzsource$,$ str$)$:

tz $=$ pytz$.$timezone$($tzsource$)$

time $=$ tz$.$localize$($time$)$

else:

time $=$ time.replace$($tzinfo$=$tzsource.tzinfo$)$

return time

pass

def daytime$($time$,$daycycle$)$:

$"""$

Returns true if the time takes place during the day.

A time is during the day if it is after sunrise but before sunset, as

indicated by the daycycle dicitionary.

A daycycle dictionary has keys for several years $($as int$).$ The value for

each year is also a dictionary, taking strings of the form $\text{'}$mm$-$dd$\text{'}.$ The

value for that key is a THIRD dictionary, with two keys "sunrise" and

"sunset". The value for each of those two keys is a string in $24-$hour

time format.

For example, here is what part of a daycycle dictionary might look like:

$"2015"$: $\{$

$"01-01"$: $\{$

"sunrise": $"07$:$35",$

"sunset": $"16$:$44"$

$\},$

$"01-02"$: $\{$

"sunrise": $"07$:$36",$

"sunset": $"16$:$45"$

$\},$

$...$

$\}$

In addition, the daycycle dictionary has a key 'timezone' that expresses the

timezone as a string. This function uses that timezone when constructing

datetime objects from this set. If the time parameter does not have a timezone,

we assume that it is in the same timezone as the daycycle dictionary

Parameter time: The time to check

Precondition: time is a datetime object

Parameter daycycle: The daycycle dictionary

Precondition: daycycle is a valid daycycle dictionary, as described above

$"""$

# HINT: Use the code from the previous exercise to get sunset AND sunrise

# Add a timezone to time if one is missing $($the one from the daycycle$)$

try:

date$\_$key $=$ f$"\{$time$.$month:$02$d$\}-\{$time$.$day:$02$d$\}"$

year$\_$key $=$ str$($time$.$year$)$

tz $=$ pytz$.$timezone$($daycycle$[\text{'}$timezone$\text{'}])$

if time.tzinfo is None:

time $=$ tz$.$localize$($time$)$

sunrise $=$ str$\_$to$\_$time$($f$"\{$year$\_$key$\}-\{$date$\_$key$\}\{$daycycle$[$year$\_$key$][$date$\_$key$][\text{'}$sunrise$\text{'}]\}",$ tz$)$

sunset $=$ str$\_$to$\_$time$($f$"\{$year$\_$key$\}-\{$date$\_$key$\}\{$daycycle$[$year$\_$key$][$date$\_$key$][\text{'}$sunset$\text{'}]\}",$ tz$)$

if sunrise is None or sunset is None:

return None

return sunrise $<=$ time $<$ sunset

except:

return None

pass