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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 tabs_or_spaces(physical_line, indent_char):
 r"""Never mix tabs and spaces. The most popular way of indenting Python is with spaces only. The second-most popular way is with tabs only. Code indented with a mixture of tabs and spaces should be converted to using spaces exclusively. When invoking the Python command line interpreter with the -t option, it issues warnings about code that illegally mixes tabs and spaces. When using -tt these warnings become errors. These options are highly recommended! Okay: if a == 0:\n a = 1\n b = 1 E101: if a == 0:\n a = 1\n\tb = 1 """

    indent = INDENT_REGEX.match(physical_line).group(1)
    for offset, char in enumerate(indent):
        if char != indent_char:
            return offset, "E101 indentation contains mixed spaces and tabs"