A minimal translation of the awsume bash file for the fish shell.

awsume.fish

#!/usr/bin/env fish

function awsume
    set AWS_VARS "AWS_SECRET_ACCESS_KEY" "AWS_SESSION_TOKEN" "AWS_SECURITY_TOKEN" "AWS_ACCESS_KEY_ID" "AWS_REGION" "AWS_DEFAULT_REGION" "AWS_PROFILE" "AWS_DEFAULT_PROFILE" "AWSUME_PROFILE"

    set AWSUME (string split " " (awsumepy))
    set AWSUME_FLAG "$AWSUME[1]"

    if test $AWSUME_FLAG = "usage:"
        awsumepy -h
    else if test $AWSUME_FLAG = "Version"
        awsumepy -v
    else if test $AWSUME_FLAG = "Listing..."
        awsumepy -l
    else if test $AWSUME_FLAG = "Auto"
        for var in $AWS_VARS
            set -e $var
        end

        set -gx AWS_PROFILE $AWSUME_FLAG[2]
        set -gx AWS_DEFAULT_PROFILE $AWSUME_FLAG[2]
        set -gx AWSUME_PROFILE $AWSUME_FLAG[3]

        #TODO
        #run the background autoAwsume process
        #autoAwsume & disown
    else if test $AWSUME_FLAG = "Kill"
        for var in $AWS_VARS
            set -e $var
        end
    else if test $AWSUME_FLAG = "Stop"
        if test "auto-refesh-$AWSUME[2]" = "$AWS_PROFILE"
            set -e AWS_PROFILE
            set -e AWS_DEFAULT_PROFILE
        end
    else if test "$AWSUME_FLAG" = "Awsume"
        for var in $AWS_VARS
            set -e $var
        end

        set -gx AWS_ACCESS_KEY_ID $AWSUME[2]
        set -gx AWS_SECRET_ACCESS_KEY $AWSUME[3]

        if test "$AWSUME[4]" != "None"
            set -gx AWS_SESSION_TOKEN $AWSUME[4]
            set -gx AWS_SECURITY_TOKEN $AWSUME[4]
        end

        if test "$AWSUME[4]" != "None"
            set -gx AWS_REGION $AWSUME[5]
            set -gx AWS_DEFAULT_REGION $AWSUME[5]
        end

        #TODO
        #if enabled, show the exact commands to use in order to assume the role we just assumed
        #<insert code here>

        set -gx AWSUME_PROFILE $AWSUME[6]
    end
end

This was very helpful. I will point out this doesn't pass any params to awsumepy so line 6 needs changing to set AWSUME (string split " " (awsumepy $argv)) to enable changing to other profiles.