title: Call python function from robot framework
body: <p>I'm trying to figure out what am I doing wrong,
  I want to get the result of a specific python function.</p>
  
  <p>This is my Resources.robot file:</p>
  
  <pre><code>*** Settings ***
  Library                           resources_func.py
  
  *** Keywords ***
  Test Time
      ${time_delta}=                get time period        ${Time}
  </code></pre>
  
  <ul>
  <li>${Time} is defined but isn't relevant to my question</li>
  </ul>
  
  <p>and this is my python script:</p>
  
  <pre><code>import re
  from dateutil.parser import parse
  
  class TimeTests(object):
      def get_time_period(timestamp):
          timestamps = re.findall(r'[0-9][0-9]:[0-9][0-9]', timestamp)
          a = parse(timestamp[0])
          b = parse(timestamp[1])
          res = (b - a)
          res = res.seconds / 60
          return res
  </code></pre>
  
  <p>This is the error I'm getting:</p>
  
  <pre><code>No keyword with name 'get time period' found.
  </code></pre>
  
  <p>Any ideas?</p>