AttributeError: 'str' object has no attribute 'items'

*** Settings ***
Library     RequestsLibrary
Library     Collections
Library     OperatingSystem

*** Variables ***
${baseUrl}      https://simple-books-api.glitch.me
${headers}      Content-Type=application/json;charset=utf-8   Authorization=Bearer TOKEN


*** Test Cases ***
OrderBook
create session  mysession   ${baseUrl}  verify=true
${body}=    create dictionary       bookId=1  customerName=John Doe
LOG TO CONSOLE     ${body}
${response}=    post on session    mysession   /orders     data=${body}    headers=${headers}
log to console  ${response}

log to console    ${response.status_code}
log to console    ${response.content}

#validations
${res_body}=    convert to string   ${response.content}
should contain    ${res_body}   true
#should contain    ${res_body}   {{bookId}}

I want to send a POST command through robot framework but keep getting
AttributeError: ‘str’ object has no attribute ‘items’

Can someone help me what i’m doing wrong in my code?
I feel like the fault is in the key:value i’m sending to the API. The bookId key only accepts integers and customerName are strings

I got it working, solution here: