sympy.diff

Sympy is a Python library for symbolic mathematics. The `diff()` function in Sympy is used to compute the derivative of a mathematical expression.

To use `diff()` in Sympy, you need to follow these steps:
1. Import the `diff` function from the `sympy` module: `from sympy import diff`.
2. Define the mathematical expression for which you want to compute the derivative.
3. Use the `diff()` function by passing in the expression and the variable you want to differentiate with respect to.

Here's an example:

from sympy import symbols, diff

# Define the mathematical expression
x = symbols('x')
expr = x**3 + 2*x**2 + x

# Compute the derivative
derivative = diff(expr, x)

print(derivative)

This will output `3*x**2 + 4*x + 1`, which is the derivative of the expression `x**3 + 2*x**2 + x` with respect to `x`.