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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_indented_block(prefix_lines):
 """Returns an integer. The return value is the number of lines that belong to block begun on the first line. Parameters prefix_lines : list of basestring pairs Each pair corresponds to a line of SHPAML source code. The first element of each pair is indentation. The second is the remaining part of the line, except for trailing newline. """

    prefix, line = prefix_lines[0]
    len_prefix = len(prefix)

    # Find the first nonempty line with len(prefix) <= len(prefix)
    i = 1
    while i < len(prefix_lines):
        new_prefix, line = prefix_lines[i]
        if line and len(new_prefix) <= len_prefix:
            break
        i += 1

    # Rewind to exclude empty lines
    while i - 1 > 0 and prefix_lines[i - 1][1] == '':
        i -= 1

    return i