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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 read(cls, f):
 """Read header from file. Headers end with length and then 1 blank line."""

    url = None

    line = f.readline()
    if not line:
      # EOF
      return None
    while not line.startswith(cls.LENGTH_HEADER):
      if line.startswith(cls.URI_HEADER):
        url = line[len(cls.URI_HEADER):].strip()
      line = f.readline()

    # Consume empty separator
    f.readline()

    # Read content
    length = int(line.split(':')[1])

    return cls(url, length)