Return an instance of Legendre that is the definite integral of the
current series. Refer to legint for full documentation.
Parameters :
m : non-negative int
The number of integrations to perform.
k : array_like
Integration constants. The first constant is applied to the
first integration, the second to the second, and so on. The
list of values must less than or equal to m in length and any
missing values are set to zero.