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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _get_section(name, source):
 # type: (str, str) -> Optional[str] """Extract the named section from the source. Args: name: The name of the section to extract (e.g. "Usage"). source: The usage string to parse. Returns: A string containing only the requested section. If the section appears multiple times, each instance will be merged into a single section. """

    pattern = re.compile(
        '^([^\n]*{name}[^\n]*\n?(?:[ \t].*?(?:\n|$))*)'.format(name=name),
        re.IGNORECASE | re.MULTILINE)
    usage = None
    for section in pattern.findall(source):
        usage = _merge_section(usage, section.strip())
    return usage