How to merge $2$ dataframe in python, I am getting below error

import pandas as pd

# Step $1$: Reading Data

airports$\_$df $=$ pd$.$read$\_$csv$(\text{'}/$Users$/$sureshvelusamy$/$Documents$/$Karthika$/$PY scripts$/$Airport$\_$Codes.csv$\text{'})$

tickets$\_$df $=$ pd$.$read$\_$csv$(\text{'}/$Users$/$sureshvelusamy$/$Documents$/$Karthika$/$PY scripts$/$Tickets$.$csv$\text{'})$

flights$\_$df $=$ pd$.$read$\_$csv$(\text{'}/$Users$/$sureshvelusamy$/$Documents$/$Karthika$/$PY scripts$/$Flights$.$csv$\text{'})$

# Step $2$: Removing Duplicates

cleaned$\_$flights$\_$df$=$flights$\_$df$.$drop$\_$duplicates$()$

cleaned$\_$tickets$\_$df$=$tickets$\_$df$.$drop$\_$duplicates$()$

cleaned$\_$airports$\_$df$=$airports$\_$df$.$drop$\_$duplicates$()$

#Filters

Roundtrip$\_$Tickets $=$ cleaned$\_$tickets$\_$df$[$tickets$\_$df$[\text{'}$ROUNDTRIP$\text{'}]==1]$

filtered$\_$flights$\_$df $=$ cleaned$\_$flights$\_$df $[$cleaned$\_$flights$\_$df $[\text{'}$CANCELLED$\text{'}]==0]$

flight$\_$tickets$=$filtered$\_$flights$\_$df$.$join$($Roundtrip$\_$Tickets, on$=(\text{'}$ORIGIN$\text{'},$ 'DESTINATION'$),$ how$=$'left'$)$

print $($flight$\_$tickets$)$ Error: ValueError Traceback $($most recent call last$)$ Cell In$[17],$ line $3315$ filtered$\_$flights$\_$df $=$ cleaned$\_$flights$\_$df $[$cleaned$\_$flights$\_$df $[\text{'}$CANCELLED$\text{'}]==0]17$ #check$=$filtered$\_$flights$\_$df$["$ORIGIN$"].$str$.$len$().$max$()18$ #check$=$filtered$\_$flights$\_$df$["$ORIGIN$"].$str$.$len$().$min$()19$ #check$=$cleaned$\_$tickets$\_$df$["$ORIGIN$"].$str$.$len$().$max$()(...)31$ #Merging data $32$ #flight$\_$tickets $=$pd$.$merge$($filtered$\_$flights$\_$df$,$Roundtrip$\_$Tickets, on$=(\text{'}$ORIGIN$\text{'},$ 'DESTINATION'$),$ how$=$'left'$)--->33$ flight$\_$tickets$=$filtered$\_$flights$\_$df$.$join$($Roundtrip$\_$Tickets, on$=(\text{'}$ORIGIN$\text{'},$ 'DESTINATION'$),$ how$=$'left'$)34$ print $($flight$\_$tickets$)$ File $/$Library$/$Frameworks$/$Python$.$framework$/$Versions$/3\mathrm{.}13/$lib$/$python$3\mathrm{.}13/$site$-$packages$/$pandas$/$core$/$frame$.$py:$10757,$ in DataFrame.join$($self$,$ other, on$,$ how, lsuffix, rsuffix, sort, validate$)10747$ if how $==$ "cross": $10748$ return merge$(10749$ self, $10750$ other, $(...)10755$ validate$=$validate, $10756)>10757$ return merge$(10758$ self, $10759$ other, $10760$ left$\_$on$=$on$,$

$...$

$1610)1611$ right$\_$on $=[$None$]*$ n $1612$ elif right$\_$on is not None: ValueError: len$($left$\_$on$)$ must equal the number of levels in the index of "right"