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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 common_start(strings):
 """Returns start sub-string that is common for all given strings Parameters strings: List of strings \tThese strings are evaluated for their largest common start string """


    def gen_start_strings(string):
        """Generator that yield start sub-strings of length 1, 2, ..."""

        for i in xrange(1, len(string) + 1):
            yield string[:i]

    # Empty strings list
    if not strings:
        return ""

    start_string = ""

    # Get sucessively start string of 1st string
    for start_string in gen_start_strings(max(strings)):
        if not all(string.startswith(start_string) for string in strings):
            return start_string[:-1]

    return start_string