Creates a gptool help xml file.

def create(filename, task, alias):
    """Creates a gptool help xml file."""

    metadata = ET.Element('metadata', {'xml:lang': 'en'})
    tool = ET.SubElement(metadata, 'tool', name=task.name,
                         displayname=task.display_name,
                         toolboxalias=alias)

    summary = ET.SubElement(tool, 'summary')
    summary.text = ''.join((HTML_BEGIN, task.description, HTML_END))

    parameters = ET.SubElement(tool, 'parameters')
    for task_param in task.parameters:
        param = ET.SubElement(parameters, 'param',
                              name=task_param['name'],
                              displayname=task_param['display_name']
                             )
        dialog_ref = ET.SubElement(param, 'dialogReference')
        dialog_ref.text = ''.join((HTML_BEGIN, task_param['description'], HTML_END))
        python_ref = ET.SubElement(param, 'pythonReference')
        python_ref.text = ''.join((HTML_BEGIN, task_param['description'], HTML_END))

    dataIdInfo = ET.SubElement(metadata, 'dataIdInfo')
    searchKeys = ET.SubElement(dataIdInfo, 'searchKeys')
    keyword1 = ET.SubElement(searchKeys, 'keyword')
    keyword1.text = 'ENVI'
    keyword2 = ET.SubElement(searchKeys, 'keyword')
    keyword2.text = task.name
    idCitation = ET.SubElement(dataIdInfo, 'idCitation')
    resTitle = ET.SubElement(idCitation, 'resTitle')
    resTitle.text = task.name
    idAbs = ET.SubElement(dataIdInfo, 'idAbs')
    idAbs.text = ''.join((HTML_BEGIN, task.description, HTML_END))
    idCredit = ET.SubElement(dataIdInfo, 'idCredit')
    idCredit.text = '(c) 2017 Exelis Visual Information Solutions, Inc.'
    resTitle.text = task.name
    tree = ET.ElementTree(metadata)
    tree.write(filename)