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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 build_agency(pfeed):
 """ Given a ProtoFeed, return a DataFrame representing ``agency.txt`` """

    return pd.DataFrame({
      'agency_name': pfeed.meta['agency_name'].iat[0],
      'agency_url': pfeed.meta['agency_url'].iat[0],
      'agency_timezone': pfeed.meta['agency_timezone'].iat[0],
    }, index=[0])