documentation for symbolic series function is wrong/misleading

[was]

Consider:

sage: f(x) = log(x)
sage: f.series?
Definition:     f.series(self, symbol, order)
Docstring:
    
       Return the power series expansion of self in terms of the variable
       symbol to the given order.
    
       INPUT:
    
       INPUT:
    
       * ``symbol`` - a variable
    
       * ``order`` - an integer
    
       OUTPUT:
    
       * a power series
    
       To truncate the power series and obtain a normal expression, use
       the truncate command.
    
       EXAMPLES:
    
       We expand a polynomial in x about 0, about 1, and also truncate it
       back to a polynomial:
    
          sage: g = f.series(x, 4); g
          3 + (-5)*x + (-sin(y))*x^2 + 1*x^3
          sage: g.truncate()
          x^3 - x^2*sin(y) - 5*x + 3
          sage: g = f.series(x==1, 4); g

This is wrong in that:

• the first input should not be called "symbol", since it can also be a symbolic expression of the form variable==number.

• the description of the first argument "symbol" in the INPUT block says it has to be a variable, but the examples, etc., clearly shows it doesn't have to be.

[was]

I couldn't think of a better name than "symbol". Oh well.

[burcin]

Looks good to me.

[jdemeyer]

According to ​http://sagemath.org/doc/developer/conventions.html#docstring-markup-with-rest-and-sphinx, the INPUT and OUTPUT blocks should not be indented.

[was]

Thanks; fixed.