<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
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<USER_TASK:>
Description:
 def validate_pipeline(url, pipeline_id, auth, verify_ssl):
 """Validate a pipeline and show issues. Args: url (str):
 the host url in the form 'http://host:port/'. pipeline_id (str):
 the ID of of the exported pipeline. auth (tuple):
 a tuple of username, and password. verify_ssl (bool):
 whether to verify ssl certificates Returns: dict: the response json """


    validate_result = requests.get(url + '/' + pipeline_id + '/validate', headers=X_REQ_BY, auth=auth, verify=verify_ssl)
    validate_result.raise_for_status()
    previewer_id = validate_result.json()['previewerId']
    poll_validation_status(url, pipeline_id, previewer_id, auth, verify_ssl)

    preview_result = requests.get(url + '/' + pipeline_id + '/preview/' + validate_result.json()['previewerId'], headers=X_REQ_BY, auth=auth, verify=verify_ssl)
    logging.debug('result content: {}'.format(preview_result.content))

    return preview_result.json()