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Write a function that returns an n x m matrix with elements that have the following values.
• The value of each element in the first row is the number of the column.
• The value of each element in the first column is the number of the row.
• The rest of the elements each has a value equal to the sum of the element above it and element to the left.
• The function must return a sensible error if the user does not input exactly two arguments
• The function should be well commented
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