<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _is_inline(self, element):
 """Return True if an element is inline."""

        if element.tag not in {etree.Comment, etree.ProcessingInstruction} and element.tag.lower() in self.inline_elements:
            return True
        return False